Control device for a dual-fuel internal combustion engine

Abstract

The invention relates to a control device (100) for a dual-fuel internal combustion engine which can be operated in a mono-fuel mode with a liquid fuel, preferably a diesel fuel, or in a dual-fuel mode with the liquid fuel and a gaseous fuel, preferably a hydrogen fuel. The control device (100) comprises: a liquid fuel control unit (10) for controlling, in a closed-loop and / or open-loop manner, a metering of the liquid fuel in the mono-fuel mode or dual-fuel mode; and a gas fuel control unit (20) for controlling, in a closed-loop and / or open-loop manner, a metering of the gaseous fuel in the dual-fuel mode. The liquid fuel control unit (10) is designed to repeatedly check whether at least one switchover condition for switching over between the mono-fuel mode and the dual-fuel mode is satisfied, and preferably to initiate the switchover if the at least one switchover condition is satisfied. The invention also relates to: a method for controlling a duel-fuel internal combustion engine, which method is performed by the control device; and a vehicle, in particular a watercraft, or a stationary application, comprising a dual-fuel internal combustion engine and the control device.

Description

[0001] Control device for a dual-fuel internal combustion engine

[0002] Description

[0003] The invention relates to a control device for a dual-fuel internal combustion engine, a method for controlling a dual-fuel internal combustion engine which is carried out by the control device, and a vehicle, in particular a watercraft, or a stationary application comprising a dual-fuel internal combustion engine and the control device.

[0004] Diesel engines are widely used in shipping due to their operational reliability and the high energy content of diesel fuel.

[0005] To achieve CCh reductions, new technologies are also required in shipping, but these are difficult to introduce in the conservative environment.

[0006] Therefore, "alternative propulsion" systems on ships are currently only known in a few isolated cases. Especially when the required travel time is several hours with a corresponding range, there is still no economically viable alternative to the diesel engine. While the use of diesel-like "green fuels" is technically very easy to manage, the fuels are not yet available at competitive prices and in sufficient quantities.

[0007] Electric propulsion systems are unlikely to replace fossil fuels in shipping. The energy required is usually too high and the energy storage densities too low.

[0008] Purely hydrogen-based solutions, such as fuel cells or combustion engines, are considered disruptive in the traditional shipping sector due to a lack of long-term experience. The lack of hydrogen infrastructure also creates high risks for the operation of pure hydrogen propulsion systems on ships. A further problem is the greater space and weight required for tank systems for hydrogen as an energy carrier compared to the widely used diesel fuel. As a result, only smaller quantities of hydrogen can be bunkered on board. This inevitably limits the operating time. This could have fatal consequences in the event of unplanned changes in the mission profile (e.g., extreme weather conditions, route changes, emergency operations such as firefighting or salvage), leading to the consumption of fuel and thus the failure of all propulsion systems.

[0009] Dual-fuel internal combustion engines are known as an "intermediate solution," in which part of the liquid fuel, usually diesel, is replaced by a gaseous fuel such as hydrogen. In addition, such dual-fuel internal combustion engines can be operated exclusively with the liquid fuel. Dual-fuel internal combustion engines therefore offer the possibility of dimensioning large, expensive, and heavy hydrogen tanks to the size required in "normal" conditions. Fuel reserves can be stored in the usual amount in the form of diesel. In the event of faults or when the hydrogen is depleted, full drive power remains available in pure and proven diesel operation.

[0010] In such dual-fuel internal combustion engines, it is important to ensure the highest possible operational reliability at all times, both during normal operation with only the liquid fuel and during operation with metered gaseous fuel. Therefore, the control systems of dual-fuel internal combustion engines play a particularly important role in ensuring operational reliability.

[0011] Accordingly, it is an object of the invention to provide such a solution that at least partially avoids the disadvantages of previous solutions. In particular, it is an object of the invention to provide an improved control system for a dual-fuel internal combustion engine that, among other things, ensures the highest possible operational reliability of a dual-fuel internal combustion engine.

[0012] The problem is solved by the features of the independent claims. Advantageous further developments are specified in the dependent claims and the description.

[0013] According to a first general aspect of the invention, a control device for a dual-fuel internal combustion engine is provided, which can be operated, in particular selectively, in a mono-fuel mode with a liquid fuel, preferably a diesel fuel, or in a dual-fuel mode with the liquid fuel and a gaseous fuel, preferably a hydrogen fuel.

[0014] The control device comprises a liquid fuel control unit for regulating and / or controlling a dosage of the liquid fuel in mono-fuel mode or dual-fuel mode, and a gaseous fuel control unit for regulating and / or controlling a dosage of the gaseous fuel in dual-fuel mode.

[0015] The liquid fuel control unit is configured to repeatedly, in particular continuously, check whether at least one switching condition for switching between the mono-fuel mode and the dual-fuel mode is met. It is also possible for the liquid fuel control unit to preferably be further configured, for example, to initiate the switching when the at least one switching condition is met.

[0016] The liquid fuel control unit and the gaseous fuel control unit are expediently connected to each other via a communication link, e.g., a CAN bus (Controller Area Network). The liquid fuel control unit and the gaseous fuel control unit are designed to communicate with each other via the communication link and / or to coordinate switching between the mono-fuel mode and the dual-fuel mode.

[0017] Switching from mono-fuel mode to dual-fuel mode involves activating the metering of the gaseous fuel (e.g., directly or indirectly into a combustion chamber of the dual-fuel engine). Switching from dual-fuel mode to mono-fuel mode involves deactivating the metering of the gaseous fuel. Activation and deactivation are conveniently controlled by the gas fuel control unit. The (conventional) introduction of the liquid fuel (into the combustion chamber of the dual-fuel engine) is conveniently carried out in both dual-fuel mode and mono-fuel mode.

[0018] The term "control device" or "control unit" can appropriately refer to electronics (e.g., with microprocessor(s) and data memory) that, depending on its configuration, can perform control and / or regulation tasks and / or processing tasks. Even if the term "control" is used herein, it can also appropriately include or mean "regulation" or "control with feedback" and / or "processing."

[0019] The present disclosure thus provides a control device for a dual-fuel internal combustion engine that ensures high operational reliability of the dual-fuel internal combustion engine. Switching between the two modes of the dual-fuel internal combustion engine only occurs when certain conditions are met, with the liquid fuel control unit acting as the master control unit. Safety-critical conditions caused by an unintentional switchover can thus be prevented. The control device thus comprises safety logic that can react to possible irregularities and thus regulate and control operation in one of the two modes or a switchover between the two modes. This ensures the highest possible operational reliability, in particular an operational reliability that is essentially also present in conventional internal combustion engines designed exclusively for operation with liquid fuel.In this way, the advantages of the known technology for liquid fuels, such as diesel technology, can be combined with the dual-fuel technology, which leads to significantly reduced CCh emissions.

[0020] Furthermore, a technology is provided with which a known internal combustion engine, designed only for operation with a liquid fuel, can be converted into a dual-fuel internal combustion engine with minimal modifications. For this purpose, the existing (liquid fuel) control unit of the internal combustion engine can be reused, e.g., using at least one adapted data set. To enable operation in dual-fuel mode, only an additional control unit, namely the gaseous fuel control unit, is required. Thus, the existing control system can simply be expanded and does not need to be completely replaced for operation in dual-fuel mode.

[0021] The liquid fuel control unit can in particular be an electronic engine control unit (ECU). The liquid fuel control unit can (as standard) be permanently active (i.e. permanently in operation) during operation of the dual-fuel internal combustion engine. This advantageously makes it possible to continue to install a control unit that is intended for conventional internal combustion engines that are only designed to run on liquid fuel, whereby an adapted data set is used. The adapted data set enables the internal combustion engine to be operated as usual in mono-fuel mode with the application unchanged. On the other hand, the internal combustion engine can also be operated in dual-fuel mode, whereby the liquid fuel control unit can be used both to initiate a switchover between the two modes and to monitor orControl of relevant conditions and parameters that enable operation of the internal combustion engine in one of the two modes.

[0022] Initially, i.e., when starting the dual-fuel internal combustion engine, the dual-fuel internal combustion engine can preferably always be started in mono-fuel mode. Subsequently, the liquid fuel control unit can check, preferably in addition to the liquid fuel control unit's self-diagnosis, whether the at least one switching condition for switching from mono-fuel mode to dual-fuel mode is met (and thus metering of the gaseous fuel is permitted). According to one embodiment, the at least one switching condition for switching from mono-fuel mode to dual-fuel mode can include exceeding and / or falling below a threshold value of at least one predetermined threshold value of at least one physical variable of the dual-fuel internal combustion engine, preferably a pressure and / or a temperature, faultless operation of the liquid fuel control unit, and / or faultless operation of the gaseous fuel control unit.Thus, the control device can check conditions and initiate metering of the gaseous fuel by switching to dual-fuel mode only when the checked conditions are met, thus ensuring the operational safety of the dual-fuel internal combustion engine.

[0023] According to one embodiment, a switch from mono-fuel mode to dual-fuel mode can be initiated by the following sequence if the at least one switch condition (for switching from mono-fuel mode to dual-fuel mode) is met: a) the liquid fuel control unit sends an enable message to the gas fuel control unit that switching to dual-fuel mode is permitted, and / or b) the gas fuel control unit sends a request message, preferably in response to the enable message, to the liquid fuel control unit requesting a switch from mono-fuel mode to dual-fuel mode, and / or c) the liquid fuel control unit sends a feedback message, preferably in response to the request message, to the gas fuel control unit that a switch from mono-fuel mode to dual-fuel mode is initiated.

[0024] The predefined sequence and the associated coordination between the two control units thus prevent safety-critical conditions caused by an unintentional switching of the operating mode or by a switching at a time when operational safety cannot be guaranteed.

[0025] According to one embodiment, the liquid fuel control unit can be configured to perform a check of the data content of the request message using a checksum check for integrity and a rolling counter check for timeliness, and to send the feedback message if the check is successful. These safety precautions can thus further increase operational reliability to prevent miscommunication between the two control units. The liquid fuel control unit can further be configured to only send the feedback message (and thus only implement the request to switch to dual-fuel mode) if the at least one switching condition for switching from mono-fuel mode to dual-fuel mode is met. Otherwise, the request can be discarded.

[0026] The feedback message may further comprise (i.e., a content of the feedback message may include) that the switchover from the mono-fuel mode to the dual-fuel mode occurs, at least one (combustion-relevant) parameter for a liquid fuel metering device is set for the dual-fuel mode, and / or a metering of the gaseous fuel is to be carried out by the gaseous fuel control unit.

[0027] According to one embodiment, the gaseous fuel control unit can be configured to check at least one gaseous fuel-specific switching condition and / or the content of the release message and to send the request message if the at least one gaseous fuel-specific switching condition is met and / or the content of the release message satisfies at least one predetermined criterion. These safety precautions can thus further increase operational reliability, with the gaseous fuel control unit being able to perform the task of checking the gaseous fuel or components provided for guiding and / or metering the gaseous fuel. The gaseous fuel control unit can thus check components and / or functions that are not present in a conventional internal combustion engine and are therefore not typically taken into account by the liquid fuel control unit.

[0028] Switching from mono-fuel mode to dual-fuel mode can be done with a shake hand.

[0029] According to one embodiment, the liquid fuel control unit and / or the gas fuel control unit can be configured to initiate a switch from dual-fuel mode to mono-fuel mode (or to remain in mono-fuel mode) if and / or as soon as at least one of the following switch conditions (for a switch from dual-fuel mode to mono-fuel mode) is present: a faulty and / or interrupted communication connection between the liquid fuel control unit and the gas fuel control unit, faulty operation of the liquid fuel control unit, e.g. a faulty sensor of the liquid fuel control unit, faulty operation of the gas fuel control unit, e.g. a faulty sensor of the gas fuel control unit, a limit value violation of at least one predetermined limit value of at least one physical variable of the dual-fuel internal combustion engine, preferably a pressure and / or a temperature, e.g.a boost pressure of a charge air below a predetermined limit boost pressure and / or a pressure in a gaseous fuel metering device outside a predetermined pressure range, an insufficient amount of gaseous fuel in a gaseous fuel tank, a leak through which the gaseous fuel escapes, and / or a faulty sensor for detecting a leak through which the gaseous fuel escapes.

[0030] The switching conditions, e.g., the limit value violation, can be monitored by a suitable sensor device that is connected by signaling to the control device, in particular to the liquid fuel control unit and / or the gaseous fuel control unit.

[0031] If one of the switching conditions (for switching from dual-fuel mode to mono-fuel mode) is met, metering of the gaseous fuel can be prevented and a switch from dual-fuel mode to mono-fuel mode can be initiated (in particular, essentially immediately). The switch from dual-fuel mode to mono-fuel mode can occur (essentially immediately) and / or be initiated as soon as one of the switching conditions (for switching from dual-fuel mode to mono-fuel mode) is met and / or as soon as the liquid fuel control unit and / or the gaseous fuel control unit signals the switch and / or the presence of one of the switching conditions.

[0032] The switchover from dual-fuel mode to mono-fuel mode can be initiated by: a) a withdrawal of at least one of the release message, the request message and / or the feedback message, preferably directly and / or without a further message, b) a sequence identical to the sequence for switching from mono-fuel mode to dual-fuel mode, and / or c) a withdrawal of the release message, the request message and the feedback message in a sequence different from the sequence for switching from mono-fuel mode to dual-fuel mode.

[0033] Furthermore, a user can be informed when at least one switching condition (for switching from dual-fuel mode to mono-fuel mode) is met. For this purpose, the control device can be signal-connected to a display device for warning that at least one switching condition is met.

[0034] According to one embodiment, the dual-fuel internal combustion engine can be operated with speed control in mono-fuel mode and in dual-fuel mode. A speed and / or torque of the dual-fuel internal combustion engine can be regulated and / or controlled by the liquid fuel control unit in mono-fuel mode and in dual-fuel mode. The speed and / or torque can be regulated, for example, by the metered (and preferably injected) amount of liquid fuel.

[0035] The liquid fuel control unit can be configured to determine, e.g., calculate, a target torque for, in particular selectively, operating the dual-fuel internal combustion engine in mono-fuel mode and in dual-fuel mode for a predetermined (and / or received) target speed and / or a predetermined (and / or received) pedal value (of a pedal and / or a control computer of a vehicle powered by the dual-fuel internal combustion engine, preferably a watercraft, or a stationary application). Because the liquid fuel control unit is responsible for monitoring or regulating the speed and determining a target torque in both modes, an existing safety concept of the liquid fuel control unit for continuous speed monitoring can advantageously be retained.

[0036] The liquid fuel control unit can be configured to receive the specified target speed from an external (marine) electronics system and / or a control computer, e.g., via the CAN bus and / or a 4-20 mA input. The specified target speed and / or a target torque can be requested, e.g., by a user via an input device, e.g., a control lever or pedal and / or an input and display device of the control computer.

[0037] Furthermore, it is also possible for the liquid fuel control unit to be configured to receive a target torque and / or the specified pedal value, e.g., a relative pedal value between 0% and 100%, from the external (marine) electronic system and / or the control computer. The liquid fuel control unit can also be configured to determine the target torque depending on the received pedal value.

[0038] According to one embodiment, the liquid fuel control unit can be signal-connected to a liquid fuel metering device of the dual-fuel internal combustion engine, preferably a common-rail injection system, for metering the liquid fuel. The liquid fuel metering device can have nozzles and / or injectors for metering and preferably injecting the liquid fuel, in particular into a combustion chamber of the dual-fuel internal combustion engine. The nozzles and / or injectors of the liquid fuel metering device can be controllable (directly or indirectly) by the liquid fuel control unit.

[0039] The gas fuel control unit can be signal-connected to a gas fuel metering device of the dual-fuel internal combustion engine for metering the gaseous fuel. The gas fuel metering device can have nozzles and / or injectors for metering and preferably injecting the gaseous fuel, in particular directly or indirectly, into a combustion chamber of the dual-fuel internal combustion engine. The nozzles and / or injectors of the gas fuel metering device can be regulated and / or controlled (directly or indirectly) by the gas fuel control unit.

[0040] The gas fuel control unit can be configured to activate the gas fuel metering device, in particular the nozzles and / or injectors, when switching from mono-fuel mode to dual-fuel mode (and to leave them activated in dual-fuel mode). The gas fuel control unit can further be configured to deactivate the gas fuel metering device, in particular the nozzles and / or injectors, when switching from dual-fuel mode to mono-fuel mode (and to leave them deactivated in mono-fuel mode).

[0041] According to one embodiment, the liquid fuel control unit can be configured to regulate and / or control at least one parameter of the liquid fuel metering device. The at least one parameter can preferably comprise at least one metering start time, a metering duration, a metering pressure, a metering number, and / or a metered quantity of the liquid fuel to be metered. Thus, the at least one parameter can be set as optimally as possible according to, among other things, the desired speed and / or the desired torque and the mode of the dual-fuel internal combustion engine. Alternatively or additionally, the gaseous fuel control unit can be configured to regulate and / or control at least one parameter of the gaseous fuel metering device. The at least one parameter can preferably comprise at least one metering start time, a metering duration, a metering pressure, a metering number, and / or a metered quantity of the gaseous fuel to be metered.Thus, at least one parameter can be set as optimally as possible according to the desired speed and / or the desired torque.

[0042] According to one embodiment, at least one (combustion-relevant) parameter of the liquid fuel metering device can be determined, regulated, and / or controlled by the liquid fuel control unit as a function of at least one stored characteristic map, preferably dependent on an engine operating point of the dual-fuel internal combustion engine, and preferably an actual speed, an actual torque, and / or an actual metered amount. The at least one characteristic map can be stored, for example, in a memory of the liquid fuel control unit.

[0043] According to one embodiment, the at least one stored characteristic map can comprise at least one characteristic map for the mono-fuel mode and at least one characteristic map for the dual-fuel mode. Thus, specific settings of the at least one parameter can advantageously be stored for both modes. Thus, selective operation in mono-fuel mode or dual-fuel mode with, for example, essentially identical performance of the dual-fuel internal combustion engine can be provided while simultaneously ensuring operational reliability.

[0044] According to one embodiment, when switching between the mono-fuel mode and the dual-fuel mode, a switch can be made between the at least one characteristic map for the mono-fuel mode and the at least one characteristic map for the dual-fuel mode for determining the at least one parameter (of the liquid fuel metering device). The at least one parameter can be switched successively, preferably along a transition curve (from a parameter value of the mono-fuel mode to a parameter value of the dual-fuel mode or from a parameter value of the dual-fuel mode to a parameter value of the mono-fuel mode). The transition curve can be adapted (separately) for each of the at least one parameters. This advantageously ensures the most optimal transition possible during each change of operating mode without a significant loss of power of the dual-fuel internal combustion engine.According to one embodiment variant, the liquid fuel control unit can be designed to regulate and / or control the at least one parameter of the liquid fuel metering device in order to increase or limit heat emission of the metered, gaseous fuel during combustion of the metered, liquid fuel and the metered, gaseous fuel to achieve a predetermined target speed and / or a predetermined torque in dual-fuel mode, preferably so that a smaller amount of nitrogen oxide, NO. Xthan occurs in mono-fuel mode and / or knocking combustion is avoided. Thus, the use of gaseous fuel not only results in significant CO2 savings, but also in a reduction of NOx and / or particulate emissions. This advantageously allows, for example, an IMO Tier III ("International Maritime Organization Tier III") emissions certification to be maintained even in dual-fuel mode.

[0045] According to one embodiment, the gaseous fuel control unit can be configured to regulate and / or control the at least one parameter of the gaseous fuel metering device in dual-fuel mode as a function of an engine operating point of the dual-fuel internal combustion engine. The gaseous fuel control unit can also be configured to receive at least one message containing the engine operating point from the liquid fuel control unit.

[0046] The at least one parameter of the gaseous fuel metering device can be determined, regulated, and / or controlled by the gaseous fuel control unit depending on stored data, e.g., at least one stored gaseous fuel characteristic map, and the engine operating point of the dual-fuel internal combustion engine. The stored data can, for example, be stored in a memory of the gaseous fuel control unit. Thus, the at least one parameter of the gaseous fuel metering device can be adjusted as optimally as possible according to the engine operating point.

[0047] According to one embodiment, the control device may further be designed to detect a leak through which the gaseous fuel escapes.

[0048] The control device can be signal-connected to a sensor system for detecting the leak. A leak can be detected if a detected leak gas mass flow, particularly during operation of the dual-fuel internal combustion engine, is above a predetermined threshold. The predetermined threshold can, for example, be between 40 g / min and 60 g / min, preferably 48 g / min, and is thus preferably only about half as high as in known automotive standards. The sensor system thus advantageously detects a leak much earlier than a sensor system, e.g., a hydrogen sensor, in an engine room in which the dual-fuel internal combustion engine is located could, since the engine room ventilation required for normal operation would immediately dilute the small amount of hydrogen below a flammable concentration.

[0049] Alternatively or additionally, a leak can be detected if a pressure in the gaseous fuel metering device is below a predetermined pressure threshold.

[0050] Leakage detection can be carried out for the dual-fuel internal combustion engine during operation (dynamic leakage test) and when the dual-fuel internal combustion engine is switched off (static leakage test).

[0051] According to a further general aspect of the invention, a method for controlling a dual-fuel internal combustion engine is provided, which can be operated, in particular selectively, in a mono-fuel mode with a liquid fuel, preferably a diesel fuel, or in a dual-fuel mode with the liquid fuel and a gaseous fuel, preferably a hydrogen fuel. The method is carried out by a control device as disclosed herein.

[0052] According to a further general aspect of the invention, a vehicle, in particular a watercraft, or a stationary application, comprising a dual-fuel internal combustion engine, which is operable, in particular selectively, in a mono-fuel mode with a liquid fuel, preferably a diesel fuel, or in a dual-fuel mode with the liquid fuel and a gaseous fuel, preferably a hydrogen fuel, and a control device as disclosed herein is provided.

[0053] The previously described embodiments, variants, and features of the invention can be combined with one another as desired. Further details and advantages of the invention are described below with reference to the accompanying drawing. It shows:

[0054] Figure 1 is a schematic view of a control device according to an embodiment of the present disclosure.

[0055] Figure 1 schematically shows the control device 100 for a dual-fuel internal combustion engine, which can be operated, in particular selectively, in a mono-fuel mode with a liquid fuel, preferably a diesel fuel, or in a dual-fuel mode with the liquid fuel and a gaseous fuel, preferably a hydrogen fuel.

[0056] The control device 100 comprises a liquid fuel control unit 10 for regulating and / or controlling a dosage of the liquid fuel in mono-fuel mode or dual-fuel mode, and a gaseous fuel control unit 20 for regulating and / or controlling a dosage of the gaseous fuel in dual-fuel mode.

[0057] The liquid fuel control unit 10 is designed to repeatedly check whether at least one switching condition for switching between the mono-fuel mode and the dual-fuel mode is met, and preferably to initiate the switching when the at least one switching condition is met.

[0058] Switching from mono-fuel mode to dual-fuel mode involves activating the metering of the gaseous fuel (e.g., directly or indirectly into a combustion chamber of the dual-fuel internal combustion engine). Switching from dual-fuel mode to mono-fuel mode involves deactivating the metering of the gaseous fuel. Activation and deactivation are expediently adjustable and / or controllable by the gaseous fuel control unit 20.

[0059] The liquid fuel control unit 10 and the gaseous fuel control unit 20 are signal-connected to each other via a communication connection, e.g., a CAN bus 4. For this purpose, the liquid fuel control unit 10 may comprise a communication interface 11, and the gaseous fuel control unit 20 may comprise a communication interface 21, with the communication interface 11 and the communication interface 21 communicating with each other via the communication connection.

[0060] The liquid fuel control unit 10 can be signal-connected to a liquid fuel metering device 17 of the dual-fuel internal combustion engine, preferably a common rail injection system, for metering the liquid fuel.

[0061] The liquid fuel metering device 17 can have nozzles and / or injectors for metering and preferably injecting the liquid fuel. The nozzles and / or injectors of the liquid fuel metering device 17 can be regulated and / or controlled by the liquid fuel control unit 10. The liquid fuel control unit 10 can be configured to regulate and / or control at least one parameter of the liquid fuel metering device 17. The at least one parameter can include at least a metering start time, a metering duration, a metering pressure, a metering number, and / or a metered quantity of the liquid fuel to be metered.

[0062] The gas fuel control unit 20 can be signal-connected to a gas fuel metering device 24 of the dual-fuel internal combustion engine for metering the gaseous fuel.

[0063] The gaseous fuel metering device 24 may have nozzles and / or injectors for metering and preferably injecting the gaseous fuel. The nozzles and / or injectors of the gaseous fuel metering device 24 may be adjustable and / or controllable by the gaseous fuel control unit 20. The liquid fuel metering device 17 and / or the gaseous fuel metering device 24 may each also be referred to as an output stage.

[0064] The gaseous fuel control unit 20 can be configured to regulate and / or control at least one parameter of the gaseous fuel metering device 24. The at least one parameter can include at least a metering start time, a metering duration, a metering pressure, a metering number, and / or a metered quantity of the gaseous fuel to be metered.

[0065] The at least one parameter of the liquid fuel metering device 17 can be determined, regulated and / or controlled by the liquid fuel control unit 10 as a function of at least one stored characteristic map, which is preferably dependent on an engine operating point of the dual-fuel internal combustion engine, and preferably an actual speed, an actual torque and / or an actual metered quantity.

[0066] The liquid fuel control unit 10 can be configured to determine the target torque for operating the dual-fuel internal combustion engine in mono-fuel mode and in dual-fuel mode for a predetermined target speed and / or a predetermined pedal value. The predetermined target speed can be received, for example, from an external (marine) electronics system and / or a control computer 3 via the CAN bus and / or a 4-20 mA input by the liquid fuel control unit 10 by means of its communication interface 11. To determine the target torque, the liquid fuel control unit 10 can further comprise a speed controller module 12. The speed controller module 12 can determine, in particular calculate, the necessary torque to operate the dual-fuel internal combustion engine at the desired speed. Alternatively or additionally, the liquid fuel control unit 10 can be configured to determine a predetermined target torque and / or the pedal value, e.g.a relative pedal value between 0% and 100%, from the external (marine) electronics system and / or the control computer 3. The liquid fuel control unit 10 can further be configured to determine the target torque as a function of the received pedal value, e.g., via the communication interface 11. In this case, the speed controller module 12 can be inactive or not present.

[0067] The at least one stored characteristic map can comprise at least one characteristic map for the mono-fuel mode and at least one characteristic map for the dual-fuel mode.

[0068] The determination of the target dosing quantity and other target parameters such as a target dosing start time, a target dosing pressure and / or a target dosing number of the liquid fuel (ie target values ​​of the dosing) can e.g. B. for the mono-fuel mode by means of a mono-fuel metering setpoint determination module 13 of the liquid fuel control unit 10 and for the dual-fuel mode by means of a dual-fuel metering setpoint determination module 14 of the liquid fuel control unit 10 depending on the at least one stored characteristic map for the mono-fuel mode, which is preferably dependent on an engine operating point of the dual-fuel internal combustion engine, or the at least one stored characteristic map for the dual-fuel mode, which is preferably dependent on an engine operating point of the dual-fuel internal combustion engine, and preferably the actual speed, the actual torque and / or the actual metering quantity.

[0069] The liquid fuel control unit 10 may further comprise a conversion module 16 for regulating and / or controlling the at least one further parameter of the liquid fuel metering device 17, e.g., the metering pressure and / or the metering duration, as a function of the metering setpoint values ​​determined by means of the mono-fuel metering setpoint determination module 13 or the dual-fuel metering setpoint determination module 14.

[0070] To ensure that the at least one parameter for the desired mode of the dual-fuel internal combustion engine is determined and the liquid fuel metering device 17 is correctly regulated and / or controlled accordingly, the liquid fuel control unit 10 can further comprise a switching module 15 that can be switched to the mono-fuel mode or the dual-fuel mode, respectively. The gaseous fuel control unit 20 can be configured to regulate and / or control the at least one parameter of the gaseous fuel metering device in the dual-fuel mode depending on an engine operating point of the dual-fuel internal combustion engine. Preferably, the gaseous fuel control unit 20 can further be configured to receive at least one message comprising the engine operating point from the liquid fuel control unit 10.

[0071] The determination of a target dosing quantity and other target parameters such as a target dosing start time, a target dosing pressure and / or a target dosing number of the gaseous fuel (ie target dosing values) can be carried out for the dual-fuel mode, for example, by means of a dosing target value determination module 22 of the gas fuel control unit 20 depending on the engine operating point of the dual-fuel internal combustion engine.

[0072] The gaseous fuel control unit 20 may further comprise a conversion module 23 for regulating and / or controlling the at least one further parameter of the gaseous fuel metering device 24, e.g., the metering pressure and / or the metering duration, as a function of the metering target values ​​determined by means of the metering target value determination module 22.

[0073] Thus, the liquid fuel control unit 10 and the gaseous fuel control unit 20 are configured to determine and change the necessary parameters of the liquid fuel metering device 17 and the gaseous fuel metering device 24, respectively, according to the mode and the desired speed and / or the desired torque of the dual-fuel internal combustion engine.

[0074] If the liquid fuel metering device 17 is a common rail injection system, the ignition and combustion of a mixture of the gaseous fuel and air in the combustion chambers can be optimally designed, in particular with significantly changed metering start times (ie injection times), metering pressures (ie rail pressures) and metering quantities (ie injection quantities).

[0075] In this combustion process, the auto-ignition of the liquid fuel, in particular a diesel fuel, is used to also ignite the gaseous fuel, in particular a hydrogen fuel. This simultaneously results in homogeneous combustion of the preferably uniformly mixed gaseous fuel in the cylinder combustion chamber of the dual-fuel internal combustion engine, as well as heterogeneous, diffusion-controlled combustion of a mixture of the liquid fuel and air, as is known from conventional internal combustion engines, in particular diesel engines. Since the gaseous fuel accounts for the majority of the combustion energy at low engine loads, the injection of the liquid fuel can be adjusted to optimally control the combustion of the gaseous fuel.In addition to the timing and quantity of the pilot and main injections, it is important to optimize the metering pressure of the common rail injection system, which regulates and / or controls the penetration of the liquid fuel injection spray and its atomization. This allows the autoignition point to be precisely adjusted to achieve the best possible heat release from the combustion of the gaseous fuel. The highest resulting flame temperatures remain below a threshold above which rapid NO formation occurs. x -formation occurs. Under the conditions described, the dual-fuel combustion process produces smaller amounts of nitrogen oxide than the mono-fuel combustion of the liquid fuel.

[0076] At higher engine loads and thus increased combustion chamber temperatures and pressures, the mixture of gaseous fuel and air burns faster, making it more susceptible to knocking. Consequently, the injection parameters are modified to limit heat dissipation and thus prevent knocking. If the injection parameters were adopted unchanged from the pure mono-fuel combustion of the liquid fuel, higher flame speeds and heat dissipation would result, resulting in higher nitrogen oxide formation than in mono-fuel operation at the same engine operating point.

[0077] A switchover from mono-fuel mode to dual-fuel mode can be initiated by the following sequence if at least one switchover condition is met: a) Sending of an enable message by the liquid fuel control unit 10 to the gaseous fuel control unit 20 that switching to dual-fuel mode is permitted, b) Sending of a request message, preferably in response to the enable message, by the gaseous fuel control unit 20 to the liquid fuel control unit 10 to request a switchover from mono-fuel mode to dual-fuel mode, and c) Sending of a feedback message, preferably in response to the request message, by the liquid fuel control unit 10 to the gaseous fuel control unit 20 that a switchover from mono-fuel mode to dual-fuel mode is initiated.

[0078] The liquid fuel control unit 10 and / or the gaseous fuel control unit 20 can thus coordinate the switching via the communication connection. The at least one switching condition for switching from mono-fuel mode to dual-fuel mode can include exceeding and / or falling below a predetermined threshold value of at least one physical variable of the dual-fuel internal combustion engine, preferably a pressure and / or a temperature, faultless operation of the liquid fuel control unit 10, and / or faultless operation of the gaseous fuel control unit 20.

[0079] The liquid fuel control unit 10 can be configured to perform a check of the data content of the request message using a checksum check for integrity and a rolling counter for timeliness. The feedback message is only sent if the check is successful. The request message can thus be checked for integrity and timeliness.

[0080] Furthermore, the gas fuel control unit 20 can check at least one gas fuel-specific switching condition and / or a content of the release message and only send the request message when the at least one gas fuel-specific switching condition is met and / or the content of the release message meets at least one predetermined criterion.

[0081] The liquid fuel control unit 10 and / or the gaseous fuel control unit 20 can further be configured to initiate a switch from the dual-fuel mode to the mono-fuel mode (or to remain in the mono-fuel mode) if and / or as soon as at least one of the following switchover conditions exists: a faulty and / or interrupted communication connection between the liquid fuel control unit 10 and the gaseous fuel control unit 20, faulty operation of the liquid fuel control unit 10, e.g., a faulty sensor of the liquid fuel control unit 10, faulty operation of the gaseous fuel control unit 20, e.g., a faulty sensor of the liquid fuel control unit 20, a limit value violation of at least one predetermined limit value of at least one physical variable of the dual-fuel internal combustion engine, preferably a pressure and / or a temperature, e.g.,a boost pressure of a charge air below a predetermined limit boost pressure and / or a pressure in a gaseous fuel metering device 24 outside a predetermined pressure range, an insufficient amount of gaseous fuel in a gaseous fuel tank, a leak through which the gaseous fuel escapes, and a faulty sensor system 30 for detecting a leak through which the gaseous fuel escapes.

[0082] In addition to the parameters already monitored in mono-fuel mode, further monitoring can be added in dual-fuel mode. As soon as the liquid fuel control unit 10 or the gaseous fuel control unit 20 detects one of the errors or limit value violations listed above, the metering of gaseous fuel to the dual-fuel internal combustion engine can be prevented. The liquid fuel control unit 10 or the gaseous fuel control unit 20 can coordinate the immediate switchback to mono-fuel mode. The switchover from dual-fuel mode to mono-fuel mode can occur (essentially immediately) as soon as one of the switchover conditions (for a switchover from dual-fuel mode to mono-fuel mode) is met and / or as soon as the liquid fuel control unit 10 and / or the gaseous fuel control unit 20 signals the switchover and / or the presence of one of the switchover conditions. For this purpose, the switchover can be initiated, for example,preferably be initiated directly and / or without a further message by withdrawing at least one of the release message, the request message and / or the feedback message.

[0083] In the event of errors detected by the liquid fuel control unit 10, such as insufficient boost pressure or a deviating rail pressure, the liquid fuel control unit 10 can perform the necessary diagnostics and error responses. Thus, in mono-fuel mode, the dual-fuel internal combustion engine exhibits the same error responses as a conventional internal combustion engine designed exclusively for operation with liquid fuel.

[0084] In the event of errors detected by the gaseous fuel control unit 20, in particular errors in the gaseous fuel inlet circuit, such as a leak or a sensor error, it is also possible to switch back to the mono-fuel mode and the dual-fuel internal combustion engine can continue to provide the required power without interruption.

[0085] For this purpose, the control device 100 can further be designed to detect a leak through which the gaseous fuel escapes.

[0086] To increase the operational reliability of the gaseous fuel inlet circuit, leak detection for the dual-fuel engine can be performed both during operation (dynamic leak test) and when the dual-fuel engine is shut down (static leak test). If a leak is detected, an error flag can be set, the metering of the gaseous fuel can be prevented, and a user can be informed.

[0087] To detect the leak, the control device 100 can be connected to a sensor 30 via signal technology.

[0088] In a dynamic leak test, a leak can be detected if a detected leak gas mass flow is above a predetermined threshold.

[0089] With a static leak test, even the smallest leaks can be detected before the dual-fuel engine is operated, thus preventing operation in dual-fuel mode. The user can be notified so that corrective measures can be initiated before larger leaks occur.

[0090] Alternatively or additionally, a leak can be detected if the pressure in the gaseous fuel metering device 24 is below a predetermined pressure threshold. The pressure in the gaseous fuel metering device 24, in particular at its nozzles and / or injectors, can be monitored repeatedly, in particular continuously, and also used to detect low-pressure leaks or flow deviations. Should a reduced flow of gaseous fuel to the dual-fuel internal combustion engine occur, the pressure would drop, for example, at the nozzles and / or injectors. The control device can report this, for example, with an error flag, whereupon the user is informed and the dual-fuel internal combustion engine can be immediately switched to safe mono-fuel mode.

[0091] The invention is not limited to the preferred embodiments described above. Rather, a multitude of variants and modifications are possible, which also utilize the inventive concept and therefore fall within the scope of protection. In particular, the invention also claims protection for the subject matter and features of the subclaims, independent of the claims referred to. In particular, the individual features of the independent claims are each disclosed independently of one another. In addition, the features of the subclaims are also disclosed independently of all features of the independent claims. List of reference symbols

[0092] 3 (Marine) electronic system and / or command computer

[0093] 4 CAN bus

[0094] 10 Liquid fuel control unit

[0095] 11 Liquid fuel control unit communication interface

[0096] 12 Speed ​​controller module

[0097] 13 Mono-fuel dosing setpoint determination module of the liquid fuel

[0098] control unit

[0099] 14 Dual-fuel dosing setpoint determination module of the liquid fuel

[0100] control unit

[0101] 15 Switching module

[0102] 16 Implementation module of the liquid fuel control unit

[0103] 17 Liquid fuel dosing device

[0104] 20 Gas fuel control unit

[0105] 21 Gas fuel control unit communication interface

[0106] 22 Dosing setpoint determination module of the gas fuel control unit

[0107] 23 Implementation module of the gas fuel control unit

[0108] 24 Gas fuel metering device

[0109] 30 Sensor technology

[0110] 100 control device

Claims

Patent claims 1. Control device (100) for a dual-fuel internal combustion engine, which can be operated in a mono-fuel mode with a liquid fuel, preferably diesel fuel, or in a dual-fuel mode with the liquid fuel and a gaseous fuel, preferably hydrogen fuel, wherein the control device (100) comprises: a liquid fuel control unit (10) for regulating and / or controlling a metering of the liquid fuel in mono-fuel mode or dual-fuel mode, and a gaseous fuel control unit (20) for regulating and / or controlling a metering of the gaseous fuel in dual-fuel mode, characterized in that the liquid fuel control unit (10) is configured to repeatedly check whether at least one switching condition for switching between the mono-fuel mode and the dual-fuel mode is met, and preferably to initiate the switching when the at least one switching condition is met.

2. Control device (100) according to claim 1, wherein the at least one switching condition for switching from mono-fuel mode to dual-fuel mode comprises exceeding and / or falling below a threshold of at least one predetermined threshold of at least one physical quantity of the dual-fuel internal combustion engine, preferably a pressure and / or a temperature, faultless operation of the liquid fuel control unit (10) and / or faultless operation of the gas fuel control unit (20).

3. Control device (100) according to claim 1 or 2, wherein a switch from mono-fuel mode to dual-fuel mode can be initiated by the following sequence when at least one switchover condition is met: a) sending a release message by the liquid fuel control unit (10) to the gas fuel control unit (20) indicating that switching to dual-fuel mode is permitted, b) sending a request message, preferably in response to the release message, by the gas fuel control unit (20) to the liquid fuel control unit (10) to request a switch from mono-fuel mode to dual-fuel mode, and / or c) Sending a feedback message, preferably in response to the request message, from the liquid fuel control unit (10) to the gas fuel control unit (20) indicating that a switchover from mono-fuel mode to dual-fuel mode is initiated. Control device (100) according to claim 3, wherein the liquid fuel control unit (10) is configured to perform a check of the data content of the request message for integrity by means of a checksum check and for recency by means of a rolling counter, and to send the feedback message if the check is successful. Control device (100) according to claim 3 or 4, wherein the gas fuel control unit (20) is configured to check at least one gas fuel-specific switchover condition and / or content of the enable message and to send the request message.if at least one gas-fuel-specific switching condition is met and / or the content of the release message meets at least one predetermined criterion. Control device (100) according to one of the preceding claims, wherein the liquid fuel control unit (10) and / or the gas fuel control unit (20) are configured to initiate a switch from dual-fuel mode to mono-fuel mode if and / or as soon as at least one of the following switching conditions is present: a faulty and / or interrupted communication link between the liquid fuel control unit (10) and the gas fuel control unit (20), a faulty operation of the liquid fuel control unit (10), a faulty operation of the gas fuel control unit (20), a limit violation of at least one predetermined limit value of at least one physical quantity of the dual-fuel internal combustion engine, preferably a pressure and / or a temperature,A control device (100) according to one of claims 3 to 6, wherein the switch from dual-fuel mode to mono-fuel mode can be initiated by a) revoking at least one of the release message, the request message and / or the feedback message, preferably directly and / or without a further message, b) an identical sequence to the sequence for switching from mono-fuel mode to dual-fuel mode, and / or c) a retraction of the release message, the request message and the feedback message in a different sequence to the sequence for switching from mono-fuel mode to dual-fuel mode.

8. Control device (100) according to one of the preceding claims, wherein a speed and / or a torque of the dual-fuel internal combustion engine in mono-fuel mode and in dual-fuel mode is adjustable and / or controllable by the liquid fuel control unit (10), and / or wherein the liquid fuel control unit (10) is configured to determine a target torque for operating the dual-fuel internal combustion engine in mono-fuel mode and in dual-fuel mode for a predetermined target speed and / or a predetermined pedal value.

9. Control device (100) according to one of the preceding claims, wherein a) the liquid fuel control unit (10) is connected to a liquid fuel metering device (17) of the dual-fuel internal combustion engine, preferably a common-rail injection system, for metering the liquid fuel, and / or b) the gas fuel control unit (20) is connected to a gas fuel metering device (24) of the dual-fuel internal combustion engine for metering the gaseous fuel.

10. Control device (100) according to claim 9, wherein a) the liquid fuel control unit (10) is configured to regulate and / or control at least one parameter of the liquid fuel metering device (17), preferably wherein the at least one parameter comprises at least a metering start time, a metering duration, a metering pressure, a metering number and / or a metering quantity of the liquid fuel to be metered, and / or b) the gas fuel control unit (20) is configured to regulate and / or control at least one parameter of the gas fuel metering device (24), preferably wherein the at least one parameter comprises at least a metering start time, a metering duration, a metering pressure, a metering number and / or a metering quantity of the gaseous fuel to be metered.

11. Control device (100) according to claim 10, wherein the at least one parameter of the liquid fuel metering device (17) depends on at least one stored, by The operating map of the dual-fuel engine is dependent on the engine operating point and preferably on an actual speed, actual torque and / or actual metering quantity, and can be determined, regulated and / or controlled by the liquid fuel control unit (10). Control device (100) according to claim 11, wherein the at least one stored operating map comprises at least one operating map for the mono-fuel mode and at least one operating map for the dual-fuel mode. Control device (100) according to claim 12, wherein, during a switch between the mono-fuel mode and the dual-fuel mode, a switch is performed between the at least one operating map for the mono-fuel mode and the at least one operating map for the dual-fuel mode to determine the at least one parameter, and wherein the at least one parameter is switched successively, preferably along a transition curve.Control device (100) according to one of claims 10 to 13, wherein the liquid fuel control unit (10) is configured to regulate and / or control at least one parameter of the liquid fuel metering device (17) in order to increase or limit heat dissipation of the metered gaseous fuel during combustion of the metered liquid fuel and the metered gaseous fuel to achieve a predetermined target speed and / or target torque in dual-fuel mode, to ensure that a lower amount of nitrogen oxide is produced during combustion than in mono-fuel mode and / or that knocking combustion is avoided.Control device (100) according to any one of claims 10 to 14, wherein the gas fuel control unit (20) is configured to regulate and / or control at least one parameter of the gas fuel metering device (24) in dual-fuel mode as a function of an engine operating point of the dual-fuel internal combustion engine, preferably wherein the gas fuel control unit (20) is further configured to receive at least one message comprising the engine operating point from the liquid fuel control unit (10). Control device (100) according to any one of the preceding claims, wherein the control device (100) is further configured to detect a leak through which the gaseous fuel escapes, wherein a) the control device (100) is signal-connected to a sensor (30) for detecting the leak, and preferably a leak is detectable when a. a) detected leakage gas mass flow is above a predetermined threshold, and / or b) a leakage is detectable when a pressure in a gas fuel metering device (24) is below a predetermined pressure threshold, preferably wherein the detection of a leakage for the dual-fuel engine is feasible both during operation and when the dual-fuel engine is switched off. A method for controlling a dual-fuel engine that can be operated in a mono-fuel mode with a liquid fuel, preferably diesel fuel, or in a dual-fuel mode with the liquid fuel and a gaseous fuel, preferably hydrogen fuel, wherein the method is carried out by a control device (100) according to one of the preceding claims.Vehicle, in particular watercraft, or stationary application, comprising a dual-fuel internal combustion engine that can be operated in a mono-fuel mode with a liquid fuel, preferably diesel fuel, or in a dual-fuel mode with the liquid fuel and a gaseous fuel, preferably hydrogen fuel, and a control device (100) according to any one of claims 1 to 16.

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