Method for operating an internal combustion engine and internal combustion engine

Abstract

The invention relates to a method for operating an internal combustion engine (1) having at least one combustion chamber (3) and an injector (5) associated with the combustion chamber (3) for introducing a first gaseous fuel into the combustion chamber (3), wherein a second liquid fuel is used for operating the injector (5), wherein in a start-up operation of the internal combustion engine (1) the injector (5) is actuated in at least one working cycle without complete combustion of the fuel introduced into the combustion chamber (3) via the injector (5).

Description

Technical Field

[0001] The present invention relates to a method for operating an internal combustion engine and an internal combustion engine designed to operate by means of such method. Background Technology

[0002] An internal combustion engine operating in this manner has at least one combustion chamber and an injector associated with the combustion chamber, the injector being designed to: introduce a first gaseous fuel into the combustion chamber; and use a second liquid fuel to operate the injector, for example as a control oil for manipulating the injector or as a sealing oil for sealing the injector. If the injector is configured as a dual-material injector and is designed to introduce an ignition fuel, in addition to the first gaseous fuel, to the combustion chamber for igniting the first gaseous fuel, then—additionally or as an alternative to its use as control oil and / or sealing oil—the second liquid fuel is used as the ignition fuel.

[0003] The following problem exists: various malfunctions can lead to an increase in the mass fraction of the second liquid fuel in the combustion chamber, such as unintended leakage of control and / or isolation oils, or damage determined by the structural type or wear of the injector. The second liquid fuel typically has a higher calorific value than the first gaseous fuel. Therefore, the unintended increase in energy input is expected to cause mechanical damage to the internal combustion engine. This risk of unintended entry of the increased amount of second liquid fuel into the combustion chamber is particularly high when adjusting the injectors after the engine has stopped. Summary of the Invention

[0004] The purpose of this invention is to create a method for operating an internal combustion engine and an internal combustion engine in which the aforementioned disadvantages are at least to a lesser extent present or avoided.

[0005] This objective is achieved by providing the teachings of this technology, particularly the teachings of the independent claims and the embodiments disclosed in the dependent claims and the specification.

[0006] This objective is achieved, in particular, by manipulating the injector during the start-up and operation of the internal combustion engine, in at least one working cycle, while avoiding complete combustion of the fuel introduced into the combustion chamber via the injector. Advantageously, the second liquid fuel accumulated in the injector is thus discharged into the combustion chamber, either unburned or at least not completely burned, especially during engine shutdown. In this way, unacceptably high final combustion pressures are avoided, particularly during engine start-up and operation, thereby also reducing, and preferably preventing, the risk of component damage. By manipulating the injector in accordance with the invention, the injector is, in particular, to a certain extent, allowed to inject freely. This specifically means that undesirable leakage of the second liquid fuel is eliminated before the internal combustion engine is put into operation and / or normal combustion begins in the combustion chamber.

[0007] Fuel is understood here as a combustible substance or a mixture of combustible substances. A mixture of combustible substances includes at least one combustible substance.

[0008] Gaseous fuels are, particularly, combustible substances or mixtures of combustible substances in a gaseous state under normal conditions, i.e., particularly at 25°C and 1013 mbar. The first gaseous fuel preferably contains at least one of the following substances or is composed of substances selected from methane, propane, and hydrogen. In a preferred design, the first gaseous fuel is natural gas, particularly liquefied natural gas (LNG) or compressed natural gas (CNG), biogas, biogas, landfill gas, process gas from the chemical industry, process gas or exhaust gas from the steel, mining, or metallurgical industries, associated gas, flare gas, lean gas, or a special gas.

[0009] Liquid fuel is understood in particular as a combustible substance or mixture of combustible substances that is liquid under normal conditions, especially at 25°C and 1013 mbar. A second liquid fuel is preferably ignition oil, particularly diesel oil or dimethyl ether. Diesel oil, in particular, can be readily used as a control oil and / or isolation oil for injectors.

[0010] The first gaseous fuel is preferably used as the primary fuel for operating the internal combustion engine. This specifically means that the majority of the total chemical energy introduced into the combustion chamber in each working cycle is introduced via the first gaseous fuel, preferably greater than 80%, preferably greater than 90%, preferably greater than 95%, and preferably greater than 97% of the chemical energy introduced into the combustion chamber in each working cycle is introduced via the first gaseous fuel. Preferably, it is also feasible that 100% of the chemical energy introduced into the combustion chamber in each working cycle is introduced via the injector in the form of the first gaseous fuel. In this case, the second liquid fuel is preferably used only as a control oil and / or isolation oil for injector operation.

[0011] Preferably, a second liquid fuel can be used as (especially only as) the control oil for manipulating the injector.

[0012] Alternatively or additionally, the second liquid fuel is used (especially only as) as a separator oil for injectors.

[0013] Alternatively or additionally, a second liquid fuel is introduced into the combustion chamber as (particularly as only) an ignition fuel. Preferably, the second liquid fuel can be introduced into the combustion chamber via a separate second injector. However, in a particularly preferred design, the second liquid fuel is introduced into the combustion chamber as an ignition fuel via the same injector as the first gaseous fuel. In this case, the injector is preferably configured as a dual-material injector.

[0014] The injector preferably has fuel circuits that are at least partially fluidly separated from each other, particularly a control oil circuit and an isolation oil circuit, which can be configured at different fuel pressures, wherein the pressure in each fuel circuit is built up individually and, in particular, sequentially in time. Specifically, the fuel path for the first gaseous fuel is preferably fluidly separated from the control oil circuit and / or the isolation oil circuit within the injector, and the fuel pressure of the first gaseous fuel can be built up in time and for the desired pressure value independently of the control oil pressure and / or the isolation oil pressure.

[0015] Operating the injector specifically means manipulating (especially activating) the injector to introduce fuel, particularly the first gaseous fuel. In this way, a second liquid fuel, which may be present in an undesirable manner, can be simultaneously discharged into the combustion chamber along with the first gaseous fuel. Preferably, the injector, configured as a dual-material injector, can be additionally manipulated to introduce the second liquid fuel as an ignition fuel into the combustion chamber as well.

[0016] Operating the injector to prevent complete combustion of the fuel introduced into the combustion chamber via the injector specifically means either manipulating it so that no combustion occurs in the combustion chamber, or manipulating it so that the fuel introduced into the combustion chamber only partially burns. In either case, the manipulation is performed to ensure incomplete combustion of the fuel introduced into the combustion chamber.

[0017] During startup, the internal combustion engine is preferably driven by a starter, particularly an electric starter motor. Alternatively or additionally, the internal combustion engine may be driven by compressed gas, such as compressed air, or otherwise driven to avoid complete combustion in at least one combustion chamber. In particular, during startup, the power required to turn the internal combustion engine is not, or at least not substantially, provided by combustion in at least one combustion chamber.

[0018] At least one working cycle in which the injector is operated during startup is preferably the first working cycle in which the injector is fully operated during the commissioning of the internal combustion engine. Thus, the injector is advantageously also freely injecting during its first operation.

[0019] After the internal combustion engine has finished starting and running, the injector is preferably operated in the normal mode used for the normal operation of the internal combustion engine.

[0020] The start-up operation preferably ends after at least two to at most 20 working cycles. In particular, after at least two to at most 20 working cycles, the injector is no longer operated during the start-up operation, but is operated in the normal mode used for the normal operation of the internal combustion engine.

[0021] According to an improved form of the invention, during startup operation, at at least one operating cycle, the injector is operated at an actuation time point within that operating cycle, at which point there are no ignition conditions for the second liquid fuel in the combustion chamber. In this way, combustion of the fuel introduced into the combustion chamber is advantageously and completely prevented, especially because if no ignition conditions for the second liquid fuel are present, the first gaseous fuel generally cannot be ignited either.

[0022] Alternatively, during startup, the injector is operated at an actuation point within at least one working cycle, ensuring that the fuel introduced via the injector is at most partially converted. In this way, it is advantageously ensured that the fuel introduced into the combustion chamber is only partially burned, and never completely burned. At most partially converted fuel specifically means that the introduced fuel is not completely converted. Fuel conversion specifically means that the fuel is burned.

[0023] The operating time point is understood here, in particular, as a relative time point within a working cycle. Thus, depending on the current speed of the internal combustion engine, the operating time point can be expressed as a time after a determined reference time point within the working cycle, or a time after a determined reference event within the working cycle. The operating time point is preferably given as crankshaft angles in °KW. If the internal combustion mechanism is a two-stroke engine, then a working cycle typically extends from 0°KW to 360°KW; if the internal combustion mechanism is a four-stroke engine, then a working cycle typically extends from 0°KW to 720°KW, i.e., it includes two full crankshaft revolutions. The operating time point is preferably the injection time point or injection inlet time point, particularly also commonly referred to as the "injection start" (BOI) or injection start time point.

[0024] According to an improved form of the invention, during startup, the injector is operated in multiple working cycles while avoiding complete combustion of the fuel introduced into the combustion chamber via the injector. Specifically, the injector is preferably operated at the operation point within each of the multiple working cycles, at which the ignition conditions for a second fuel are not present in the combustion chamber, or it is further ensured that the fuel introduced via the injector is at most partially converted. If the injector is operated in this way in multiple working cycles, it is advantageously allowed to inject freely and particularly effectively, thus avoiding excessive load on the internal combustion engine with high safety through unacceptably high final combustion pressures.

[0025] Multiple work cycles are particularly preferably work cycles that follow each other directly. In particular, the work cycle is preferably the first work cycle in which the injectors are fully operated after the internal combustion engine has been commissioned.

[0026] During startup, the injector is preferably operated for at least 2 to at most 20 working cycles while avoiding complete combustion of the fuel introduced into the combustion chamber via the injector. In particular, startup operation is preferably maintained for at least 2 and at most 20 working cycles.

[0027] Alternatively or additionally, the injector can be operated multiple times during startup and operation in at least one working cycle. In particular, the injector can be operated in a clockwise manner within a single working cycle. In this way, the injector can also be freely sprayed very efficiently.

[0028] According to an improved form of the invention, during startup, the injector is operated during the valve overlap phase. This has the advantage that, on the one hand, there are certainly no ignition conditions for a second fuel during the valve overlap phase, while on the other hand, there is typically a strong outward flow from the combustion chamber during this phase, which reliably carries unburned fuel out of the combustion chamber, thus reliably avoiding unacceptably high loads on the combustion chamber. The valve overlap phase is specifically a time or crankshaft angle span within the working cycle during which the inlet valve associated with the combustion chamber for introducing fresh mass, particularly combustion air, and the outlet valve associated with the combustion chamber are opened, the outlet valve being designed to allow exhaust gas to exit the combustion chamber. In particular, the valve overlap phase preferably encompasses the crankshaft angle range of the piston's top dead center (TDC), which is capable of reciprocating displacement within the combustion chamber, wherein TDC is associated with the intake stroke of the working cycle; that is, the intake stroke of the working cycle is connected to TDC. TDC is hereinafter referred to as intake OT. The valve overlap phase preferably extends from at least 50°KW before intake OT to at most 50°KW after intake OT, preferably from at least 45°KW before intake OT to at most 45°KW after intake OT, preferably from at least 40°KW before intake OT to at most 40°KW after intake OT, and in a particularly preferred design, from at least 46°KW before intake OT to at most 43°KW after intake OT.

[0029] Alternatively, it is preferable to actuate the injector during startup after the top dead center (TDC) of the piston, which is capable of reciprocating displacement within the combustion chamber, associated with the expansion stroke. Specifically, the expansion stroke is connected to said TDC. This TDC is hereinafter referred to as expansion OT. The expansion stroke is particularly the power stroke of the working cycle. If fuel is introduced into the combustion chamber sufficiently late after expansion OT, it ensures that the fuel introduced into the combustion chamber is at least incompletely converted, i.e., at most partially converted. If necessary, combustion can even be completely avoided.

[0030] In the preferred design, during startup, the injector is operated at a power of at least 15°KW to at most 50°KW after expansion OT, preferably at least 20°KW to at most 40°KW, preferably at least 25°KW to at most 35°KW, and most preferably at 30°KW after expansion OT.

[0031] An improved form of the invention proposes selecting an actuation point based on a prediction of the maximum amount of second liquid fuel introduced via the injector, said actuation point being activated after expansion OT during start-up operation. In this way, the actuation point can be matched to the anticipated harm of the second liquid fuel to the internal combustion engine. Specifically, a prediction is created regarding the second liquid fuel introduced into the combustion chamber at most via the fuel path for the first gaseous fuel. Therefore, it is based on the assumption that a specific leakage amount of second liquid fuel seeps into the fuel path of the first gaseous fuel and is then discharged into the combustion chamber along with the first gaseous fuel when the injector is activated. This fuel quantity can be determined from bench testing or estimated based on the injector's structural type and / or wear.

[0032] Fuel quantity here is specifically understood as fuel mass.

[0033] Specifically, the timing of the operation is selected based on the ratio of the predicted maximum amount of second fuel introduced to the predetermined maximum mechanical load of the combustion chamber. In particular, the proportion of the second liquid fuel that can still burn harmlessly in the combustion chamber without causing damage can be determined by the aforementioned considerations, and the timing of the operation can be selected accordingly. In this way, it is advantageous to avoid the excessive release of unburned fuel into the internal combustion engine environment.

[0034] Preferably, a prediction of the maximum amount of fuel introduced for the second fuel is first created, from which a prediction of the combustion pressure value, particularly the combustion pressure trend over time or the maximum combustion pressure value, is further created. Then, the combustion pressure value is compared with the maximum permissible combustion pressure value describing the maximum mechanical load on the combustion chamber, particularly with the maximum permissible combustion pressure trend over time or the maximum permissible combustion pressure value. Based on this comparison, the timing of the operation is then selected in an appropriate manner so that the maximum permissible combustion pressure value is not reached, wherein preferably, it is considered that as much of the second fuel as possible remains burning in the combustion chamber and is therefore not released into the internal combustion engine environment in an unburned manner.

[0035] According to an improved form of the invention, the injector is operated only after a predetermined limit speed has been reached or exceeded during startup. In this manner, it is particularly advantageous to ensure that the fuel introduced into the combustion chamber is effectively discharged from the combustion chamber via the outlet valve. Specifically, the injector is operated only after the starter reaches a preset limit speed, following the starter's initial operating phase.

[0036] According to an improved form of the invention, the injector is operated only when the pressure in the fuel supply system for the injector reaches or exceeds the first fuel pressure limit value of the first fuel and the second fuel pressure limit value of the second fuel. In this way, it is advantageously ensured that any unwanted second liquid fuel, especially any leaked second liquid fuel, is safely discharged.

[0037] Preferably, the pressure build-up in the fuel supply system is monitored, particularly the pressure build-up of the first fuel and / or the second fuel. Specifically, the pressure development over time is monitored. In particular, the pressure build-up for different fuels, especially for different fuel circuits, is preferably built-up in a predetermined sequence. This sequence is preferably monitored. Preferably, the injector is operated only when the pressure build-up is identified as normal, especially when the pressure build-up is trending according to specific criteria, particularly within predetermined limits.

[0038] In particular, it is preferable to first construct the isolation oil pressure, then construct the control oil pressure, and finally construct the pressure in the fuel path for the first gaseous fuel.

[0039] According to an improved form of the invention, after a predetermined number of injector actuations, particularly after a predetermined number of work cycles in which injector actuation is performed, the actuation time point of the injector during startup is progressively shifted forward until combustion is detected in the combustion chamber. Specifically, the actuation time point preferably begins to progressively shift forward from a predetermined position after expansion OT. Here, shifting the actuation time point "forward" specifically means that the actuation time point begins to shift closer to expansion OT from its instantaneous position, i.e., particularly reducing the crankshaft angular distance from expansion OT. This progressively increases the pressure present in the combustion chamber at the actuation time point until ignition conditions for a second liquid fuel are present in the combustion chamber. If this is the case, the second liquid fuel is ignited, wherein the first gaseous fuel is also ignited by the second liquid fuel. Combustion occurs in the combustion chamber.

[0040] Preferably, the combustion chamber is equipped with a pressure sensor to detect the combustion chamber pressure. Specifically, the combustion chamber pressure is preferably recorded as a function of time. More specifically, a combustion chamber pressure curve or combustion pressure curve over time is preferably recorded. Combustion in the combustion chamber can be inferred based on the combustion chamber pressure, particularly the change in combustion chamber pressure over time. In particular, combustion can be identified based on the change in combustion chamber pressure, particularly the change in combustion pressure over time.

[0041] Preferably, a pressure sensor is associated with the combustion chamber, and the combustion chamber pressure is detected via the pressure sensor. In particular, it is preferable to detect the combustion chamber pressure over time. Combustion within the combustion chamber can be inferred from the combustion chamber pressure, especially its trend over time. Specifically, combustion can be identified based on the combustion chamber pressure, especially the trend of combustion pressure over time.

[0042] Preferably, the combustion chamber pressure is also monitored during the normal or conventional operation of the internal combustion engine. In a particularly preferred manner, during normal operation of the internal combustion engine, the development of the combustion chamber pressure over time, in relation to the total operating duration of the injector, is monitored based on the instantaneous control parameters of the injector. Based on determined limits, such as the absolute value of the combustion chamber pressure over time, the variance of the combustion chamber pressure over time, etc., the control timing can be adjusted backward during normal operation if necessary to protect the combustion chamber. Therefore, emergency operation of the internal combustion engine, for example, to achieve an emergency operation function (limp-home mode), is feasible, advantageously avoiding damage to the internal combustion engine. This emergency operation can advantageously be combined with reinforcing measures, such as visualization via a display device accessible to the internal combustion engine operator.

[0043] According to an improved form of the invention, when combustion in the combustion chamber is detected during or after a gradual forward shift of the operating time point, the operating time point is set at an initial operating value. Here, the initial operating value is the value of the operating time point suitable for the actual starting, starting, or actuation of the internal combustion engine, i.e., particularly the acceleration of the internal combustion engine from the starter speed up to the idle speed or rated speed, wherein the power required here is provided by combustion in at least one combustion chamber. Specifically, at this time point, the starter is mechanically disengaged from and / or deactivated from the internal combustion engine.

[0044] After reaching the idle speed or rated speed, the operating time point is preferably set at the continuous operating value. This continuous operating value is suitable for the normal or routine operation of the internal combustion engine. Specifically, the continuous operating value varies according to the current operating point of the internal combustion engine.

[0045] The method presented herein and the protective functions derived therefrom can be readily implemented via corresponding programmable functions in the control software for controlling the internal combustion engine. No additional safety measures are required to protect the departing combustion gases and / or coolant. This method is preferably integrated into the engine's start-up process. The internal combustion engine can be protected without additional protective functions, and especially without impairing normal operation.

[0046] This objective is also achieved by creating an internal combustion engine having at least one combustion chamber and an injector associated with the combustion chamber, the injector being designed to introduce a first gaseous fuel into the combustion chamber. Furthermore, the injector is designed to use a second liquid fuel to operate the injector, particularly as a control oil, as a separator oil, and / or as an ignition fuel. The internal combustion engine also has a control device effectively connected to the injector and designed to operate the injector during the start-up operation of the internal combustion engine, in at least one working cycle, while avoiding complete combustion of the fuel introduced into the combustion chamber via the injector. In particular, the control device is designed to perform the method according to the invention or according to one of the embodiments described above. With regard to the internal combustion engine, advantages already explained above regarding the method are particularly advantageous.

[0047] The internal combustion engine is preferably configured as a reciprocating piston engine. Here, the piston can reciprocate within the combustion chamber.

[0048] Preferably, an inlet valve is associated with the combustion chamber, through which fresh mass, particularly combustion air, is introduced into the combustion chamber. An outlet valve is also associated with the combustion chamber, through which exhaust gas is discharged from the combustion chamber.

[0049] Preferably, a pressure sensor is associated with the combustion chamber, the pressure sensor being designed and configured to detect the combustion chamber pressure within the combustion chamber. The pressure sensor is particularly effectively connected to a control device. The control device is preferably designed to detect the trend of combustion chamber pressure over time.

[0050] The internal combustion engine preferably has a starter, particularly an electric starter motor. The starter is designed to pull the internal combustion engine during startup.

[0051] In the preferred design, the injector is configured as a dual-material injector.

[0052] The description of the method and the description of the internal combustion engine should be understood as complementary. The internal combustion engine features explicitly or implicitly explained with respect to the method are preferably individual or combined features of preferred embodiments of the internal combustion engine. The method steps explicitly or implicitly explained with respect to the internal combustion engine are preferably individual or combined steps of preferred embodiments of the method. Preferably, the method is characterized by at least one method step that depends on at least one feature of the internal combustion engine according to the invention or at least one feature of an embodiment of the internal combustion engine. Preferably, the internal combustion engine is characterized by at least one feature that depends on at least one method step of the method according to the invention or at least one method step of a preferred embodiment of the method. Attached Figure Description

[0053] The invention will now be explained in more detail with reference to the accompanying drawings. Herein lies:

[0054] Figure 1 A schematic diagram showing one embodiment of an internal combustion engine, and

[0055] Figure 2 This is a flowchart-type schematic diagram illustrating one embodiment of a method for operating an internal combustion engine. Detailed Implementation

[0056] Figure 1 A schematic diagram of one embodiment of an internal combustion engine 1 is shown. The internal combustion engine has at least one combustion chamber 3, preferably multiple combustion chambers 3. An injector 5 is associated with the combustion chamber 3, the injector being designed to introduce a first gaseous fuel into the combustion chamber 3. The injector 5 is also designed to use a second liquid fuel for its operation, particularly as a control oil, as a separator oil, and / or as an ignition fuel.

[0057] In a preferred design, the internal combustion engine 1 is designed for dual-fuel operation, wherein a first gaseous fuel is introduced into the combustion chamber 3 as the main fuel, and the first gaseous fuel is ignited by introducing a second liquid fuel, in an ignition amount, into the combustion chamber 3 as the ignition fuel. Here, the ignition fuel may be introduced into the combustion chamber 3 via an additional, separate injector, but may also be introduced via injector 5. In a preferred design, the second liquid fuel is also introduced into the combustion chamber 3 via injector 5. Injector 5 is preferably configured as a dual-fuel injector.

[0058] The internal combustion engine 1 also includes a control device 7, which is effectively connected to the injector 5 and designed to operate the injector 5 during the start-up and operation of the internal combustion engine 1, in at least one working cycle, while avoiding complete combustion of the fuel introduced into the combustion chamber 3 via the injector 5. In this way, an undesirable amount of second liquid fuel can be discharged into the combustion chamber 3 without concern that excessive amounts of second liquid fuel in the combustion chamber 3 could damage the combustion chamber due to excessively high final combustion pressure or otherwise harm the components of the internal combustion engine 1.

[0059] Specifically, the control device 7 is designed to: operate the injector 5 at an operating time point within at least one working cycle during startup operation, at which the ignition conditions for a second fuel are not present in the combustion chamber 3, or at the operating time point also ensure that the fuel introduced via the injector 5 is converted to a maximum extent.

[0060] In particular, the control device 7 is preferably designed to operate the injector 5 during startup and multiple working cycles while avoiding complete combustion of the fuel introduced into the combustion chamber 3 via the injector 5.

[0061] The piston 9 is preferably moved in a reciprocating manner in the combustion chamber 3. The internal combustion engine 1 is preferably configured as a reciprocating piston engine.

[0062] Preferably, the inlet valve 11 for introducing fresh material into the combustion chamber 3 is associated with the combustion chamber 3. Furthermore, it is preferable to associate the outlet valve 13 for exhaust gas exiting the combustion chamber 3 with the combustion chamber 3.

[0063] The control device 7 is preferably designed to operate the injector 5 during the valve overlap phase of the inlet valve 11 and the outlet valve 13 during startup operation, particularly from 50°KW before the intake OT of the piston 9 to 50°KW after the intake OT, preferably from 45°KW before the intake OT to 45°KW after the intake OT, preferably from 40°KW before the intake OT to 40°KW after the intake OT, and preferably from 46°KW before the intake OT to 43°KW after the intake OT.

[0064] The control device 7 is preferably designed to operate the injector 5 during startup, at the top dead center of the piston 9 associated with the expansion stroke, i.e., after expansion OT, particularly at least 15°KW to at most 50°KW after expansion OT, preferably at least 20°KW to at most 40°KW after expansion OT, preferably at least 25°KW to at most 35°KW after expansion OT, and preferably 30°KW after expansion OT.

[0065] The control device 7 is preferably designed to select the timing of the operation based on a prediction of the maximum amount of fuel introduced via the injector 5 for the second liquid fuel (especially relative to the predetermined maximum mechanical load of the combustion chamber 3), at which the injector 5 is operated during startup operation after expansion OT.

[0066] A pressure sensor 15 is associated with the combustion chamber 3, the pressure sensor being configured and designed to detect the combustion chamber pressure in the combustion chamber 3. A control device 7 is effectively connected to the pressure sensor 15 and is preferably designed to detect the trend of the combustion chamber pressure in the combustion chamber 3 over time using the pressure sensor 15. The control device 7 is preferably designed to identify combustion in the combustion chamber 3 based on the detected trend of the combustion chamber pressure over time.

[0067] The internal combustion engine 1 has a starter 17, particularly an electric starter motor, designed to actuate the internal combustion engine 1 during startup. For this purpose, the starter 17 is preferably mechanically and effectively connected to the crankshaft 19 of the internal combustion engine 1, particularly driven and preferably driven. In a preferred design, the starter 17 can be mechanically disengaged from and / or deactivated after startup or at the end of startup.

[0068] Figure 2 A schematic diagram illustrating one embodiment of a method for operating an internal combustion engine 1 is shown.

[0069] Here, the method is initiated in the first step S1. At this point in time, the internal combustion engine 1 is stationary, and its rotational speed n is 0.

[0070] In the second step S2, the initiator 17— Figure 2 The starter, also known as the starter motor, is activated. In the third step S3, it is checked whether the speed of the internal combustion engine 1 has reached or exceeded a predetermined initial speed, preferably 150 rpm. Furthermore, in step S3, it is checked whether the control device 7 (referred to as the ECU) is ready. If one of the conditions is not met, the third step S3 is executed until both conditions are met.

[0071] The method is then continued in the fourth step S4 by preferably building up the pressure of the first gaseous fuel and the second liquid fuel in a predetermined order. In particular, it is preferable to build up the isolation oil pressure first, then the control oil pressure, and finally the pressure of the first gaseous fuel (also referred to as fuel gas).

[0072] In step S5, the stress build is monitored, particularly regarding the stress build over time—preferably assessing whether the stress build is proceeding too slowly—and preferably also monitoring the order of the stress builds. In step S6, the stress build is checked for proper functioning. If the stress build is found to be normal, a normal signal SIG is output.

[0073] Normal signal SIG is preferably only when Figure 1 The figure schematically illustrates, and is indicated by reference numeral 21, that the fuel supply system is activated only when the fuel pressure for the injector 5 used for the first gaseous fuel has reached or exceeded a first fuel pressure limit and for the second liquid fuel has reached or exceeded a second fuel pressure limit. The fuel supply system 21 is specifically designed for supplying fuel, particularly for supplying control oil, isolation oil, and fuel gas.

[0074] Conversely, if—refer to again Figure 2 If the pressure buildup in step S6 is deemed abnormal, pressure buildup is stopped in step S7. In step S8, pressure is released. In step S9, startup parameters are adapted, such as setting a longer time interval between fuel loops during pressure buildup, and the method then continues with a new pressure buildup in step S4.

[0075] In step S10, check whether there is a normal signal SIG, i.e. whether the pressure build-up is normal, and check whether the speed of the internal combustion engine 1 has reached or exceeded the predetermined limit speed, especially the starter speed, especially 180U / min.

[0076] The method continues in step eleven, S11, only if both conditions are met. Otherwise, the check in step ten, S10, is repeated until both conditions are met.

[0077] In step eleven, S11, the injector 5 is then operated in at least one working cycle, preferably in multiple working cycles, preferably in a clock-controlled manner, while avoiding complete combustion of the fuel introduced into the combustion chamber 3 via the injector 5, i.e., free injection of the injector. Here, preferably, fuel is introduced into the combustion chamber 3 30° KW after expansion OT.

[0078] After a predetermined number of operations of the injector 5 and / or after a predetermined number of corresponding operating cycles of the injector 5, the operation time point is progressively shifted forward in step 12, S12. Simultaneously, in step 13, the control device 7 checks whether combustion in the combustion chamber 3 has been detected. Specifically, the forward shift in step 12, S12, continues until combustion is detected in step 13, S13. If this is the case, the operation time point is set to the starting operating value in step 14, S14, and the internal combustion engine 1 is started or activated in step 15, S15.

[0079] Preferably, after the internal combustion engine 1 reaches its idle speed or rated speed, the operating time of the injector 5 is set to a continuous operating value. The continuous operating value can vary according to the current operating point of the internal combustion engine 1.

Claims

1. A method for operating an internal combustion engine (1), the internal combustion engine having at least one combustion chamber (3) and an injector (5) associated with the combustion chamber (3) for introducing a first gaseous fuel into the combustion chamber (3), wherein a second liquid fuel is used to operate the injector (5), wherein - During the start-up operation of the internal combustion engine (1), in at least one working cycle, the injector (5) is manipulated during the valve overlap phase to introduce the first gaseous fuel while avoiding complete combustion of the fuel introduced into the combustion chamber (3) via the injector (5).

2. The method according to claim 1, wherein, During the startup operation, the injector (5) is operated at an operation time point within the at least one work cycle, at the operation time point, a) There are no ignition conditions for the second liquid fuel in the combustion chamber (3), or b) Ensure that the fuel introduced via the injector (5) is converted to a maximum extent.

3. The method according to any one of the preceding claims, wherein, During the start-up operation, the injector (5) is operated in multiple working cycles to avoid complete combustion of the fuel introduced into the combustion chamber (3) via the injector (5).

4. The method according to claim 1 or 2, wherein, The valve overlap phase is a time or crankshaft angle span within the working cycle during which the inlet valve associated with the combustion chamber for introducing fresh material into the combustion chamber and the outlet valve associated with the combustion chamber are opened, the outlet valve being designed to allow exhaust gas to exit the combustion chamber.

5. The method according to claim 4, wherein, The fresh material is combustion air.

6. The method according to claim 4, wherein, The valve overlap phase is the crankshaft angle range including the top dead center of the piston, which is capable of reciprocating displacement in the combustion chamber, wherein the top dead center is associated with the intake stroke of the working cycle, such that the intake stroke of the working cycle is connected to the top dead center.

7. The method according to claim 6, wherein, The valve overlap phase extends from at least 50°KW before the top dead center to at most 50°KW after the top dead center, which is connected by the intake stroke of the working cycle.

8. The method according to claim 6, wherein, The valve overlap phase extends from at least 45°KW before the top dead center to at most 45°KW after the top dead center, which is connected by the intake stroke of the working cycle.

9. The method according to claim 6, wherein, The valve overlap phase extends from at least 40°KW before the top dead center to at most 40°KW after the top dead center, which is connected by the intake stroke of the working cycle.

10. The method according to claim 6, wherein, The valve overlap phase extends from at least 46°KW before the top dead center to at most 43°KW after the top dead center, which is connected by the intake stroke of the working cycle.

11. The method according to claim 6, wherein, During startup, within the crankshaft angle range including the piston connected to the top dead center by the expansion stroke, the injector is operated in the range of at least 15°KW to at most 50°KW after the top dead center connected by the expansion stroke.

12. The method according to claim 6, wherein, During startup, within the crankshaft angle range including the piston connected to the top dead center by the expansion stroke, the injector is operated in the range of at least 20°KW to at most 40°KW after the top dead center connected by the expansion stroke.

13. The method according to claim 6, wherein, During startup, within the crankshaft angle range including the piston connected to the top dead center by the expansion stroke, the injector is operated in the range of at least 25°KW to at most 35°KW after the top dead center connected by the expansion stroke.

14. The method according to claim 6, wherein, During startup, within the crankshaft angle range including the piston and the top dead center connected by the expansion stroke, the injector is operated 30° kW after the top dead center connected by the expansion stroke.

15. The method according to any one of claims 11 to 14, wherein, The timing of the operation is selected based on a prediction of the maximum amount of fuel introduced via the injector (5) for the second liquid fuel, at which the injector (5) is operated during the start-up operation within the crankshaft angle range including the top dead center connected by the expansion stroke.

16. The method according to claim 1 or 2, wherein, During the start-up operation, the injector (5) is operated only after the predetermined limit speed is reached or exceeded.

17. The method according to claim 1 or 2, wherein, During the start-up operation, when the pressure in the fuel supply system (21) for the injector (5) reaches or exceeds a) The first fuel pressure limit value of the first gaseous fuel, and b) The second fuel pressure limit value of the second liquid fuel Only then is the injector (5) operated.

18. The method according to claim 1 or 2, wherein, After a predetermined number of operations of the injector (5), the operation time of the injector (5) is gradually shifted forward during the start-up operation until combustion is detected in the combustion chamber (3).

19. The method according to claim 18, wherein, When combustion is detected in the combustion chamber (3) during or after the gradual forward shift of the control time point, the control time point is set to the initial operating value.

20. An internal combustion engine (1) having at least one combustion chamber (3), wherein an injector (5) for introducing a first gaseous fuel into the combustion chamber (3) is associated with the combustion chamber (3), wherein the injector (5) is designed to use a second liquid fuel to operate the injector (5), and wherein the internal combustion engine (1) has a control device (7) effectively connected to the injector (5) and designed to: during the start-up operation of the internal combustion engine (1), in at least one working cycle, manipulate the injector (5) to introduce the first gaseous fuel while avoiding complete combustion of the fuel introduced into the combustion chamber (3) via the injector (5), wherein the control device is designed to perform the method according to any one of claims 1 to 19.

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