System, control method of system, and vehicle including system

Abstract

System, control method of the system, and vehicle including the system. In particular, the present disclosure relates to an internal combustion engine system (10) for a vehicle, comprising: an internal combustion engine ICE (20) operable on a low cetane number fuel (32), the internal combustion engine having a cylinder at least partially defining a combustion chamber and an ignition source for the low cetane number fuel; a fuel injector (30) for injecting the low cetane number fuel into the combustion chamber; an ignition improver device (40) in fluid communication with the fuel injector and further configured to supply an ignition improver fluid to the low cetane number fuel; a control unit (90) configured to selectively operate the ICE in a spark ignition SI mode and a compression ignition CI mode, wherein the control unit is configured to determine ICE operating conditions and to control the ignition improver device to supply a given amount of ignition improver fluid to the low cetane number fuel based on the determined ICE operating conditions.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to combustion of low cetane number fuel in an internal combustion engine. In particular, the present disclosure relates to an internal combustion engine (ICE) system for a vehicle. Furthermore, the present disclosure relates to a method for controlling such an ICE system of a vehicle. In addition, the present disclosure relates to a vehicle comprising such an ICE system. The present disclosure can typically be applied to ICE systems used as part of the powertrain of heavy duty vehicles, such as trucks, buses and construction equipment. The present disclosure can equally be applied to other vehicles, such as cars and other light duty vehicles, but also to marine vessels and the like. Other applications are possible, for example the present disclosure in stationary power plant systems. BACKGROUND

[0002] Vehicle propulsion systems are continuously developed to meet demands from the market. A particular technical field of vehicle propulsion systems relates to emissions of exhaust gases that are harmful to the environment. Therefore, other alternatives to conventional diesel internal combustion engines are evaluated and implemented in vehicles that are more environmentally friendly. One example of such an alternative is a hydrogen internal combustion engine. Another example of such an alternative is a methanol internal combustion engine.

[0003] Furthermore, internal combustion engines are continuously developed to meet a number of other demands, at least partly related to the environment and emissions. As an example, increasing engine efficiency and reducing noise levels of ICE systems have become some of the criteria that have become more important when designing and selecting internal combustion engine (ICE) systems for heavy duty vehicles.

[0004] Furthermore, in the field of heavy duty vehicles, such as trucks, there are a number of existing environmental regulations that set specific requirements for vehicles, for example, regarding limits on maximum allowed amounts of exhaust gas pollutants.

[0005] One type of ICE system that can meet existing and future environmental regulations is a hydrogen ICE system, where combustion of hydrogen with oxygen produces water, heat and NOx as by-products. Hydrogen is a low cetane number fuel. Hydrogen can be provided as hydrogen gas or as a hydrogen fluid. Another type of ICE system that can meet existing and future environmental regulations is a methanol ICE system.

[0006] In the field of fuel systems and fuel injection systems for ICE systems, the need for increasing the efficiency of supplying fuel to the ICE is further increasing. Therefore, ICE systems often comprise fuel injection systems in the form of so-called common rail systems, in particular for ICE systems in which fuel is directly injected into the cylinders of the ICE. These types of fuel injection systems can generally be denoted as direct fuel injection systems. A typical common rail system is fluidly connected to a high pressure fuel pump which delivers fuel to a common rail via a high pressure line. The common rail is in the form of an accumulator. The term "common rail system" denotes a fuel injection system in which there is a common rail which supplies fuel to a plurality of injectors. The common rail is configured to deliver fuel to a plurality of injectors via a plurality of high pressure tubes. The system may, for example, comprise six injectors, six high pressure tubes and one common rail (for a 6 cylinder engine).

[0007] In some ICE systems, fuel is injected into the cylinders of the ICE and then ignited by a spark plug device. Other solutions for ignition of the fuel are also conceivable, depending on the type of fuel and the type of ICE.

[0008] To meet at least some of the above-mentioned needs, various engine concepts have been developed over the years, in which conventional combustion cylinders and fuel systems have been combined in several different ways to provide efficient and reliable ICE systems.

[0009] However, there is still a need for an improved ICE system capable of operating on low cetane number fuel. SUMMARY

[0010] It is an object of the present disclosure to provide increased thermodynamic efficiency over a wide operating range of an internal combustion engine system of a vehicle in which the internal combustion engine is capable of operating on low cetane number fuel. This object is at least partly achieved by an internal combustion engine system according to the first aspect of the present disclosure.

[0011] According to a first aspect of the present disclosure, there is provided an internal combustion engine system for a vehicle. The internal combustion engine system comprises an internal combustion engine (ICE) capable of operating on low cetane number fuel and having a cylinder at least partially defining a combustion chamber and an ignition source for the low cetane number fuel, a fuel injector for injecting the low cetane number fuel into the combustion chamber, an ignition improver device in fluid communication with the fuel injector and further configured to supply an ignition improver fluid to the low cetane number fuel. The internal combustion engine system further comprises a control unit configured to cause the ICE to selectively operate in a spark ignition (SI) mode and a compression ignition (CI) mode. In addition, the control unit is configured to determine an ICE operating condition and to control the ignition improver device to supply a given amount of the ignition improver fluid to the low cetane number fuel based on the determined ICE operating condition.

[0012] The present disclosure is based on the insight that many low cetane number fuels can provide a substantial reduction in CO2 emissions and a reduction in operating costs. However, many low cetane number fuels are also prone to suffer from poor auto-ignition. It is therefore an advantage to supply the low cetane number fuel with an ignition improver fluid in order to at least partly overcome the problem of poor auto-ignition of the low cetane number fuel in the combustion cylinder of the ICE system.

[0013] By providing a control unit configured to determine an ICE operating condition and to control the ignition improver device to supply a given amount of ignition improver fluid to the low cetane number fuel based on the determined ICE operating condition, a more efficient and controllable supply of ignition improver fluid can be provided, while at the same time increasing the ignitability of the low cetane number fuel in a cost-effective manner. This can be particularly beneficial for certain combinations of ignition improver fluid and low cetane number fuel. In addition, such control of the ignition improver device differs from available systems for supplying ignition improver fluid, in which the amount of ignition improver is typically chosen to be able to cope with all engine load situations of the ICE. Since lower engine loads and cold start typically will require a higher amount of ignition improver, such prior art ignition improver devices are typically associated with a high supply cost.

[0014] In addition, by providing a control unit configured to cause the ICE to selectively operate in a spark-ignition (SI) mode and a compression-ignition (CI) mode, the ICE system can be operated in a number of different ICE modes, thereby providing an efficient and reliable ICE system during different driving operations of the vehicle. As an example, the CI combustion mode with ignition improver is advantageous at high loads to achieve high efficiency and sufficient power density, while the SI combustion mode can be used at low loads without ignition improver to achieve relatively low emissions.

[0015] Thus, the proposed system provides increased thermodynamic efficiency over a wide operating range of the ICE system.

[0016] The control unit can be configured to, in response to receiving a control signal indicating a switch from the SI mode to the CI mode, control the ignition improver device to supply a given amount of ignition improver fluid to the low cetane number fuel, such that the ignition improver fluid is supplied to the low cetane number fuel during the switch from the SI mode to the CI mode. In this way, the ignition improver fluid is supplied to the low cetane number fuel just before the switch from the SI mode to the CI mode, thereby facilitating auto-ignition of the low cetane number fuel when starting the CI mode of the ICE system.

[0017] While it can be beneficial to supply the ignition improver fluid to the fuel as late as possible for controllability reasons, the ignition improver fluid can be supplied in several different ways, as described below.

[0018] The ignition improver fluid can be supplied to the low cetane number fuel at a position arranged in a fluid conduit upstream of the fuel injector. In this way, a controlled supply of ignition improver fluid to low cetane number fuel can be provided for certain types of ICE systems.

[0019] The fuel injector can be adapted to receive the low cetane number fuel and the ignition improver fluid via separate first and second inlets, such that the low cetane number fuel and the ignition improver fluid are mixed at the fuel injector. In this way, a controlled supply of ignition improver fluid to low cetane number fuel can be provided for certain types of ICE systems.

[0020] Alternatively, the fuel injector can be adapted to supply a mixed amount of low cetane number fuel and ignition improver fluid to the combustion chamber via a common outlet. For other types of ICE systems, this configuration of the fuel injector can be beneficial for improving the supply of ignition improver fluid to low cetane number fuel. In addition, this configuration can have a positive impact on the controllability of the ICE system.

[0021] The supply and control of the ignition improver fluid can be performed in several different ways. Optionally, the control unit and the ignition improver device are configured to control the supply of ignition improver fluid in accordance with one or more of the following examples.

[0022] As an example, the control unit can be configured to determine the given amount of ignition improver fluid based on a value of the determined ICE operating condition. The control unit can be configured to increase the amount of ignition improver fluid if the determined ICE operating condition corresponds to a non-favorable auto-ignition ICE condition. Additionally or alternatively, the control unit can be configured to decrease the amount of ignition improver fluid if the determined ICE operating condition corresponds to a favorable auto-ignition ICE condition.

[0023] A favorable auto-ignition ICE condition is an ICE operating condition that is favorable for auto-ignition of the low cetane number fuel when the low cetane number fuel is supplied into a combustion chamber of a cylinder of the engine. A non-favorable auto-ignition ICE condition is an ICE operating condition that is not favorable for auto-ignition of the low cetane number fuel when the low cetane number fuel is supplied into a combustion chamber of a cylinder of the engine.

[0024] The ICE operating conditions can be indicative of any of an ICE load, an ICE rotational speed value, a cylinder pressure level, and a temperature level. Such parameters and values can be stored in a memory of the control unit and / or received from the ICE system to the control unit during operation of the ICE.

[0025] The control unit can generally be configured to compare the determined ICE operating conditions with reference values to determine whether the determined ICE operating conditions are non-favorable or favorable auto-ignition ICE conditions.

[0026] Such reference values are generally determined by actual experiments, analytical derivation, computer simulation, or a combination of the above. In practice, these reference values can be represented by a look-up table (LUT) indexed by reference values. As an example, the look-up table contains data for various rotational speed values, cylinder pressure levels, and temperature levels. These reference values for rotational speed values, cylinder pressure levels, and temperature levels can be used to determine whether the determined ICE conditions are non-favorable or favorable auto-ignition ICE conditions.

[0027] As an example, the spark ignition (SI) mode corresponds to an Otto cycle mode.

[0028] As an example, the low cetane number fuel is any of hydrogen, methanol, ammonia, E85, pure ethanol, and naphtha. The hydrogen fuel can be hydrogen gas or a hydrogen fluid.

[0029] The ignition improver fluid can include a liquid or gas containing a substance that affects the auto-ignition temperature of the low cetane number fuel. Thus, the ignition improver fluid generally affects the combustion characteristics of the low cetane number fuel.

[0030] In some examples, the substance of the ignition improver fluid includes any of a nitrate salt, a nitroalkane, a nitrocarbonate, and a peroxide. This type of improver fluid can be considered more efficient than using, for example, a single fuel to improve the ignition of another fuel in a dual fuel ICE system.

[0031] The ignition improver fluid can include a combination of multiple substances.

[0032] As an example, the substance of the ignition improver fluid includes a nitrate salt, a nitroalkane, a nitrocarbonate, and a peroxide.

[0033] In some examples, the internal combustion engine (ICE) system can be a single fuel ICE system. In some examples, the internal combustion engine can thus be operated on a single fuel. A single fuel ICE system is different from a dual fuel ICE system. The single fuel can be a low cetane number fuel. In such examples, the ignition improver fluid can advantageously include a liquid or gas containing a substance that affects the auto-ignition temperature of the low cetane number fuel, wherein the substance of the ignition improver fluid comprises any one of a nitrate salt, a nitroalkane, a nitrocarbonate salt, and a peroxide. By using such an ignition improver fluid in a single low cetane number fuel ICE system operating in a CI combustion mode, a more efficient operation of the ICE system can be provided. Additionally, using this type of ignition improver fluid in a single low cetane number fuel ICE system provides a more efficient ICE system compared to a dual fuel ICE system using one of the fuels as an ignition improver compound, as such a dual fuel ICE system can typically be associated with higher fuel supply costs. Thus, the ignition improver fluid used by the single low cetane number fuel ICE system includes a substance containing any one of a nitrate salt, a nitroalkane, a nitrocarbonate salt, and a peroxide, which allows for a more efficient and controllable use of the ignition improver fluid during a CI combustion mode and / or at the above-mentioned switch from a SI mode to a CI mode.

[0034] The ignition source for operating the ICE in the SI mode can be any one of a spark plug, a glow plug, and pilot fuel injection.

[0035] The control unit can be configured to increase the amount of ignition improver fluid if the determined ICE operating condition corresponds to a low load ICE condition. The control unit can be configured to decrease the amount of ignition improver fluid if the determined ICE operating condition corresponds to a high load ICE condition.

[0036] According to a second aspect, there is provided a method for controlling an internal combustion engine system of a vehicle. The internal combustion engine system comprises an internal combustion engine (ICE) operable on a low cetane number fuel and having a cylinder at least partially defining a combustion chamber and an ignition source for the low cetane number fuel, a fuel injector for injecting the low cetane number fuel into the combustion chamber, and an ignition improver device in fluid communication with the fuel injector for supplying an ignition improver fluid to the low cetane number fuel. The method comprises operating the ICE in a spark ignition (SI) mode, determining an ICE operating condition, and based on the determined ICE operating condition, supplying a given amount of ignition improver fluid to the low cetane number fuel.

[0037] The effects and features of this second aspect of the present disclosure are largely analogous to those described above in connection with the first aspect of the present disclosure. The embodiments mentioned in relation to the first aspect of the present disclosure are largely compatible with the second aspect of the present disclosure.

[0038] The method according to the example embodiment can be performed in several different ways. According to one example embodiment, the steps of the method are performed by the control unit during use of the ICE system of the vehicle. According to one example embodiment, the steps of the method are performed in sequence. However, at least some of the steps of the method can be performed in parallel.

[0039] The method can further comprise switching from the SI mode to a compression ignition (CI) mode.

[0040] The switching from the SI mode to the CI mode can be performed during a transition period in which the ICE system can be operated in various temporary intermediate ICE modes, such as a spark-assisted CI mode or the like.

[0041] The method can further comprise increasing the amount of ignition improver fluid if the determined ICE operating condition corresponds to a non-favorable auto-ignition ICE condition.

[0042] The method can further comprise decreasing the amount of ignition improver fluid if the determined ICE operating condition corresponds to a favorable auto-ignition ICE condition.

[0043] The method can further comprise controlling the fuel injector to supply the mixed low-cetane fuel and ignition improver fluid to the combustion chamber of the cylinder.

[0044] The method can further comprise operating different cylinders in different modes based on the determined ICE operating condition.

[0045] According to a third aspect, there is provided a computer program comprising program code means for performing the steps of any of the embodiments described above in relation to the second aspect when said program is run on a computer or on a processing circuitry of a control system. The computer program can be stored or distributed on a data carrier. As used herein, a "data carrier" can be a transitory data carrier, such as a modulated electromagnetic or light wave, or a non-transitory data carrier. Non-transitory data carriers include volatile memory and non-volatile memory, such as permanent and non-permanent storage devices of the magnetic, optical or solid-state type. Still within the scope of "data carrier", such memory can be fixedly installed or portable.

[0046] According to a fourth aspect, a computer-readable medium carrying a computer program is provided, the computer program comprising a program component for executing the steps of any one of the embodiments described above with respect to the second aspect when the program component is run on a computer or on a processing circuit of a control system.

[0047] The effects and features of the third and fourth aspects are largely similar to those described above in relation to the first and second aspects.

[0048] According to a fifth aspect, a vehicle is provided that includes the internal combustion engine system according to the first aspect of the present disclosure. The effects and features of this fifth aspect of the present disclosure are largely similar to those described above in conjunction with the first disclosure. The embodiments mentioned in relation to the first aspect of the present disclosure are largely compatible with the fifth aspect of the present disclosure.

[0049] Further advantages and advantageous features of the present disclosure are disclosed in the description which follows.It will also be readily apparent that different features may be combined to create embodiments other than those described in the following, without departing from the scope of the present disclosure.

[0050] The terms used herein are used only to describe specific examples and are not intended to limit the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that when used herein, the terms "comprises", "comprising", "includes" and / or "including" refer to the presence of the stated features, integers, steps, operations, elements and / or parts, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups thereof.

[0051] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the present disclosure belongs. It should be further understood that the terms used herein should be interpreted as having a meaning consistent with their meaning in the context of this specification and the relevant art, and, unless expressly defined as such herein, should not be interpreted in an idealized or overly formal sense. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The above and other objects, features and advantages of the present disclosure will be better understood through the following detailed description of exemplary embodiments of the present disclosure, which is illustrative and not restrictive, in which:

[0053] Figure 1is a side view of a vehicle comprising an internal combustion engine (ICE) system according to an example embodiment of the present disclosure;

[0054] Figure 2 is a schematic view of further components of an ICE system according to an example embodiment of the present disclosure, wherein the ICE system can be comprised in Figure 1 the vehicle shown in

[0055] Figure 3 is a flow chart of a method for performing control of an ICE system according to an example embodiment of the present disclosure. DETAILED DESCRIPTION

[0056] The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the disclosure are shown. The disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout the specification.

[0057] With particular reference to Figure 1 , a vehicle 1 in the form of a truck is provided. The vehicle 1 comprises an internal combustion engine (ICE) system 10 for providing power to and driving the vehicle 1. Figure 1 The ICE system 10 in may further comprise an ICE 20. In the present example, the ICE system 10 is a hydrogen piston ICE system. As is generally known in the art, combustion in such a hydrogen ICE system is based on combustion of air and hydrogen. While combustion of hydrogen with oxygen can only produce water as its only product in a pure combustion process between hydrogen and oxygen, a hydrogen ICE system based on combustion of air and hydrogen will typically produce water, heat and NOx, as is generally known in the art. In addition, hydrogen can be combusted in the internal combustion engine in a wide variety of fuel-air mixtures. The hydrogen ICE system can be operated under certain conditions to produce very low emissions. The hydrogen ICE system can be operated based on hydrogen liquid or hydrogen gas.

[0058] For ease of reference, the ICE system 10 described with reference to Figures 1 to 3 is a hydrogen gas ICE system, i.e. the low cetane number fuel is hydrogen gas. However, as an alternative, the ICE system can comprise another type of ICE capable of operating on another type of low cetane number fuel. Another conceivable type of low cetane number fuel is methanol. Thus, the examples below apply equally to a methanol ICE system.

[0059] In addition, the ICE system described with reference to Figures 1 to 3 is a single fuel ICE system. Thus, the ICE system 10 is a single low cetane number fuel ICE system. Thus, the ICE system 20 is capable of operating on a single fuel in the form of a low cetane number fuel.

[0060] As Figure 1 depicted in Figure 3 Further described below, the control unit 90 is configured to perform any of a number of steps of a method for controlling the ICE system 10. Here, the control unit 90 is part of a main electronic control unit for controlling the vehicle and various parts of the vehicle.

[0061] Reference is now made to Figure 2 wherein one example embodiment of an ICE system 10 for inclusion in a vehicle is depicted as described above with reference to Figure 1 As is generally known in the art of ICE systems 10, the ICE 20 comprises a number of cylinders 14 which operate to combust a fuel 32, e.g. hydrogen, whereby the reciprocating motion of the pistons 16 within the cylinders 14 is transferred as rotational motion of the crankshaft 18. The crankshaft 18 is further coupled to a transmission (not shown) for providing torque to a drive element (not shown). In the case of heavy vehicles, e.g. trucks, the drive element is the vehicle wheels; however, the ICE 20 can also be used for other equipment, e.g. construction equipment, marine applications, etc.

[0062] Generally, each cylinder 14 is provided with a corresponding piston 16 which is connected to the crankshaft 18 of the ICE 20. The ICE system 10 further comprises an intake manifold (not shown) forming an air intake guide arranged to direct air to the cylinders 14, and an exhaust guide (not shown) arranged to direct gases from the cylinders 14.

[0063] The ICE system 10 further comprises an exhaust arrangement (not shown) which serves the purpose of transporting exhaust gases and recovering at least some of the energy in the exhaust stream to improve ICE performance.

[0064] Each cylinder 14 can further comprise at least one, typically a plurality, of intake passages for intake air at its vertical top end, and at least one, typically a plurality, of exhaust passages for exhaust gases from the combustion process occurring within the cylinder 14. The cylinder is described in conventional terms only, as its components and functions are well known in the art. The cylinder can be of in-line, V-type or any other suitable kind of construction, for example. The ICE system 10 can further comprise additional engine components and system components.

[0065] Each of the cylinders 14 is at least partially defined with a combustion chamber 15. It is also common that one end of the cylinder cavity is closed by a cylinder head. The piston 16 reciprocates within the cylinder and is connected to the crankshaft 18 such that the piston is arranged to reverse within the cylinder between top dead center and bottom dead center positions.

[0066] Here, the ICE system 10 also includes a common rail fuel injection system 24, as is generally known in the art. Figure 2 As shown, the common rail fuel injection system 24 defines a common fuel line 25 ("common rail") and is configured to supply hydrogen to the cylinders 16 through a plurality of injectors 30. Thus, the common rail fuel injection system 24 herein includes the plurality of injectors 30. The number of injectors 30 may be equal to the number of cylinders of the ICE 20. Here, the common rail fuel injection system 24 includes six injectors 30, as shown in FIG. Figure 2 The fuel injector 30 is arranged in fluid communication with the common fuel line 25 of the common rail fuel injection system 24. The common rail fuel injection system 24 is usually arranged inside the ICE 20. Therefore, in order to inject fuel into the combustion chamber of the cylinder, the ICE usually includes one or more fuel injectors 30.

[0067] In addition, the ICE 20 includes an ignition source 17. The ignition source 17 is arranged in the cylinder and at a position facing the combustion chamber. As an example, the ignition source 17 is arranged at the upper end of the combustion cylinder and is spaced apart from the fuel injector, such as Figure 2 Other arrangements of the ignition source and fuel injector are also contemplated.

[0068] Ignition source 17 is configured to ignite hydrogen gas 32 supplied via common fuel line 25. By way of example, this ignition source is a spark plug 17. A spark plug is a device used to deliver electrical current from the ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel / air mixture via an electric spark while maintaining combustion pressure within the engine. Typically, there is a corresponding spark plug in each cylinder 14, arranged to ignite the fuel and oxygen mixture in the cylinder. The hydrogen fuel is typically compressed to a certain level. The compressed air-fuel mixture is then ignited by the spark plug.

[0069] In the hydrogen ICE 20, fuel in the form of gaseous hydrogen is supplied from a fuel tank via a fuel system to the ICE 20. Therefore, the ICE system 10 includes a fuel system 50, a fuel pump 51 and a fuel conduit circuit 58, as shown in FIG. Figure 2 The fuel conduit circuit 58 is arranged and configured to receive and deliver fuel, as shown in FIG. Figure 2 As shown by the arrow in .

[0070] The fuel pump 51 is arranged and configured to pressurize the fuel to a high pressure level. The fuel pump 51 is arranged in the fuel system 50 to deliver the high pressure fuel to the fuel injectors 30 arranged in the ICE 20, as shown in FIG. Figure 2 As shown in FIG. 5 . The fuel pump 51 is of conventional type and will not be described further herein. In addition, the fuel pump 51 is in fluid communication with a fuel tank 52 for containing fuel. Figure 2As depicted in FIG, fuel pump 51 may be in fluid communication with both an inlet fuel line 55 and a fuel return line 56. Other designs and systems are also contemplated and generally used to supply fuel to ICE 20.

[0071] like Figure 2 As shown in FIG, the fuel pump 51 is in fluid communication with the common rail fuel injection system 24 via a fuel conduit circuit 58. The one or more fuel injectors 30 are adapted to receive hydrogen gaseous fuel 32 via one or more inlets. Figure 2 , the one or more fuel injectors 30 are adapted to receive hydrogen gaseous fuel 32 via an inlet 57. As an example, a fuel conduit circuit 58 includes an inlet fuel line 55 and a fuel return line 56. The inlet fuel line 55 is connected to the inlet 57 of the common rail fuel injection system 24. Thus, the fuel pump 51 is in fluid communication with the common rail fuel injection system 24 via the inlet fuel line 55 and the fuel return line 56.

[0072] Optionally, the fuel system 50 further includes a fuel filter 53 disposed in the fuel conduit loop 58. The fuel filter 53 is configured to filter the fuel. Typically, a fuel filter is a filter in the fuel line that removes dirt and other particles from the fuel and is typically made into a filter element containing filter paper. In addition, the fuel system 50 herein includes a fuel pre-filter 54 disposed in the inlet fuel line 55 of the fuel conduit loop 58, such as Figure 2 Typically, this fuel pre-filter is placed in the fuel system to separate water from the fuel and remove residues from the fuel, preventing them from being pumped into the ICE and causing oxidation, corrosion, and cavitation problems in the cylinders. This pre-filter is also useful for extending the service life of the injectors.

[0073] In addition, the ICE system 10 includes an ignition improver device 40, such as Figure 2 As shown in . The ignition improver device 40 is arranged to be in fluid communication with each of the one or more fuel injectors 30. As an example, the ignition improver device 40 is arranged to be in fluid communication with the one or more fuel injectors 30 via the common rail system 24. In addition, the ignition improver device is configured to supply an ignition improver fluid 44 to the hydrogen gaseous fuel, for example Figure 2 As shown. The ignition improver device 40 includes an ignition improver fluid tank 45 for storing an ignition improver fluid 44. The ignition improver fluid contains a substance that influences the auto-ignition of the fuel. For example, the ignition improver fluid 44 is a liquid or gas containing a substance that influences the auto-ignition of methanol fuel. In another example where the fuel is hydrogen, the ignition improver fluid 44 is a liquid or gas containing a substance that influences the auto-ignition of hydrogen fuel.

[0074] Accordingly, the ignition improver fluid generally affects the combustion characteristics of the low cetane number fuel.

[0075] As an example, the substance of the ignition improver fluid includes any one of nitrates, nitroalkanes, nitrocarbonates, and peroxides. These substances are generally known to have a positive effect on the auto-ignition of low cetane number fuels, such as methanol, hydrogen, etc.

[0076] As mentioned above, the ICE of the ICE system 10 is capable of operating on a single fuel in the form of a low cetane number fuel. In such an example, it is particularly beneficial to use a dedicated ignition improver fluid having a substance including any one of nitrates, nitroalkanes, nitrocarbonates, and peroxides.

[0077] To supply the ignition improver fluid from the ignition improver fluid tank 45 into the hydrogen gas prior to combustion of the hydrogen gas, the ICE system 10 comprises an ignition improver fluid circuit 42 extending between the ignition improver fluid tank 45 and the ICE 20, as shown in Figure 2 Optionally, there is also a fluid pump 41 arranged in the ignition improver fluid circuit 42 for directing the ignition improver fluid 44 to the one or more fuel injectors 30. In Figure 2 The ignition improver device 40 comprises the fluid pump 41, the ignition improver fluid circuit 42, the ignition improver fluid 44, and the ignition improver fluid tank 45. Other types of ignition improver devices 40 are also conceivable, depending on the type of ICE system. Furthermore, while the ignition improver device 40 is here an integral part of the fuel cell system 50, the ignition improver device 40 can equally be a separate component of the ICE system 10. The one or more fuel injectors 30 are adapted to receive the ignition improver fluid 44 via the corresponding inlet 47.

[0078] Turning again to Figure 1 , the one or more fuel injectors 30 are adapted to receive the hydrogen gas fuel 32 via the inlet 57 and the ignition improver fluid 44 via the inlet 47. Accordingly, the one or more fuel injectors 30 are adapted to receive the hydrogen gas fuel 32 and the ignition improver fluid 44 via separate first and second inlets 57 and 47, respectively. In this way, the hydrogen gas fuel 32 and the ignition improver fluid 44 are mixed at the one or more fuel injectors 30.

[0079] In another example, although not shown, the ignition improver fluid 44 is supplied to the hydrogen gas fuel 32 at a location in a fluid conduit 58 arranged upstream of the one or more fuel injectors 30. Alternatively, although not shown, the fuel injectors 30 are adapted to supply a mixed amount of the hydrogen gas fuel 32 and the ignition improver fluid 44 to the combustion chamber 15 via a common outlet.

[0080] As mentioned above, the ICE system 10 comprises a control unit 90. Here, the control unit is configured to cause the ICE to selectively operate in a spark ignition (SI) mode and a compression ignition (CI) mode. As an example, the control unit 90 comprises processing circuitry configured to cause the ICE to selectively operate in a spark ignition (SI) mode and a compression ignition (CI) mode. The processing circuitry can contain software and / or algorithms containing instructions causing the ICE 20 to operate in each of the SI mode and the CI mode. As an example, the spark ignition (SI) mode corresponds to an Otto cycle mode. The Otto cycle mode is, for example, a regular four-stroke mode. In such a SI mode, a fuel-air mixture is introduced into the cylinder during the intake stroke by means of a fuel injector (hydrogen fuel and ignition improver fluid) and an intake valve (compressed air). Subsequently, the fuel-air mixture is compressed in the compression stroke. Thereafter, a combustion stroke (or power stroke) is performed (constant volume), in which the resulting gas expands. Finally, the ICE 20 performs an exhaust stroke, in which the resulting gas is expelled from the cylinder through an exhaust valve.

[0081] In the CI mode, the ICE 20 typically works according to the following sequence: fuel is injected into the charge of compressed air and ignites spontaneously by the high temperature of the introduced air due to the compression heat.

[0082] To facilitate operation of the ICE system 20, the ignition improver device 40 is configured to be controlled by the control unit 90, as further described below. In particular, the ignition improver device 40 is controlled to supply ignition improver fluid 44 to the hydrogen fluid 32 in order to facilitate ignition of the fuel when the ICE system 20 is to be operated in the SI mode. Thus, the control unit 90 is configured to control the ignition improver device 40 to supply a given amount of ignition improver fluid 44 to the hydrogen fluid 32 in response to receiving a control signal indicating a switch from the SI mode to the CI mode. Thereby, ignition improver fluid 44 is supplied to the hydrogen fluid 32 during the switch from the SI mode to the CI mode.

[0083] To minimize consumption of ignition improver fluid 44 and thus the cost of ignition improver fluid 44 used, the supply of ignition improver fluid 44 is also metered based on current engine operating conditions. As mentioned above, the ignition improver fluid 44 is introduced to the fuel system via a separate inlet 47 close to the fuel injector 30 or directly to the fuel injector 30. At low loads on the ICE 20, typically more ignition improver fluid can be needed, while at higher loads on the ICE 20, less ignition improver can be needed. Furthermore, as mentioned above, the ignition improver fluid 44 can be added to the fuel system just before the injector 30 in case of a unit injector fuel system. In case of a common rail system, the ignition improver fluid 44 can be added to the fuel system in the rail, as described above.Figure 2 As shown in Fig. 1, the ignition improver fluid 44 is typically added to the low pressure side or to the high pressure fuel rail. By adding the ignition improver fluid 44 close to the injector 30, the supply of ignition improver fluid 44 is typically facilitated in terms of controllability.

[0084] Furthermore, here the control unit 90 is further configured to determine an ICE operating condition and to control the ignition improver device 40 to supply a given amount of ignition improver fluid 44 to the hydrogen gas fluid 32 based on the determined ICE operating condition. The control unit 90 is configured to determine said given amount of ignition improver fluid 44 based on a magnitude of the determined ICE operating condition. As an example, the control unit 90 is configured to increase the amount of ignition improver fluid 44 if the determined ICE operating condition corresponds to a condition that is not favourable for the auto-ignition of the fuel, i.e. a non-favourable auto-ignition ICE condition. As an example only, said non-favourable auto-ignition ICE condition is also a low load ICE condition.

[0085] Additionally, or alternatively, the control unit 90 is configured to decrease the amount of ignition improver fluid 44 if the determined ICE operating condition corresponds to a condition that is favourable for the auto-ignition of the fuel, i.e. a favourable auto-ignition ICE condition. As an example only, said favourable auto-ignition ICE condition is also a high load ICE condition.

[0086] Since the auto-ignition of low cetane number fuels typically depends on temperature, the ICE operating condition can also typically be indicative of the temperature inside the combustion chamber, directly or indirectly. This temperature is one factor that has a direct influence on the initiation of chemical reactions to ignite the fuel. However, since different engine loads and rpm typically give different pressures, and in turn different temperatures, other ICE operating conditions can also be determined, such as pressure, engine load, etc., in order to decide whether the ICE operating condition is a non-favourable auto-ignition ICE condition or a favourable auto-ignition ICE condition.

[0087] The ICE operating condition is indicative of any one of an ICE load, an ICE speed value, a cylinder pressure level and a temperature level. Such parameters and values can be stored in a memory of the control unit and / or received from the ICE system to the control unit during operation of the ICE. As an example, the temperature level of the ICE is measured by a temperature sensor arranged inside one or more cylinders of the ICE. Similarly, the pressure level inside the cylinder, i.e. the pressure level inside the combustion chamber of the cylinder, is measured by a pressure sensor arranged in the combustion chamber. The ICE load and the ICE speed value can be measured and determined in several different ways, as is well known in the art of ICE systems.

[0088] The determined parameters and values of the ICE operating conditions can be compared to reference values. Such reference values are typically determined by actual experiments, analytical derivation, computer simulations, or a combination of the above. In practice, these reference values can be represented by a look-up table (LUT) indexed by the reference values. As an example, the look-up table contains data for various values of rotational speed, cylinder pressure level, and temperature level. These reference values of rotational speed, cylinder pressure level, and temperature level are used to determine whether the determined ICE conditions are non-favorable auto-ignition ICE conditions or favorable auto-ignition ICE conditions.

[0089] Thus, the control unit is typically configured to compare the determined ICE conditions to reference values to determine whether the ICE conditions are non-favorable auto-ignition ICE conditions or favorable auto-ignition ICE conditions.

[0090] In summary, Figure 1 and Figure 2 The example embodiments in

[0091] As mentioned above, the example embodiments described with reference to Figure 1 and Figure 2 are also applicable to ICE systems in which the low cetane number fuel is liquid phase methanol. Furthermore, the example embodiments described with reference to Figure 3 and Figure 1 are also applicable to other types of improver ignition fluids, including liquid fluids and gaseous fluids.

[0092] It should also be noted that the use of the above described ignition improver fluids (which have a substance comprising any one of a nitrate salt, a nitroalkane, a nitrocarbonate salt, and a peroxide) in the above described single low cetane number fuel ICE system allows for a more efficient and controllable use of the ignition improver fluid during the CI combustion mode and / or when switching from the SI mode to the CI mode as described above.

[0093] In Figure 2 , in which a method for controlling an internal combustion engine system 10 for a vehicle 1 is depicted, the method comprises operating the ICE 20 in a spark ignition (SI) mode and a compression ignition (CI) mode, determining ICE operating conditions, and controlling the ignition improver device 40 to supply a given amount of ignition improver fluid to the low cetane number fuel based on the determined ICE operating conditions.Figure 1 and Figure 2 A method 200 of the ICE system 20 is described. The method is generally performed by the control unit 90 during operation of the ICE system 20. The method comprises the step of operating S10 the ICE 20 in a spark ignition (SI) mode.

[0094] Further, the method comprises the step of determining S20 an ICE operating condition. Subsequently, the method comprises the step of supplying S30 a given amount of ignition improver fluid to the low cetane number fuel based on the determined ICE operating condition.

[0095] Optionally, the method further comprises switching S40 from the SI mode to a compression ignition (CI) mode.

[0096] The method can further comprise increasing the amount of ignition improver fluid 44 if the determined ICE operating condition corresponds to a non-favourable auto-ignition ICE condition.

[0097] The method can further comprise decreasing the amount of ignition improver fluid 44 if the determined ICE operating condition corresponds to a favourable auto-ignition ICE condition.

[0098] The method can further comprise controlling the fuel injectors to supply the mixed low cetane number fuel and ignition improver fluid to the combustion chamber of the cylinder.

[0099] The method can further comprise operating different cylinders in different modes based on the determined ICE operating condition.

[0100] The steps of the method are generally performed by the control system 90, as described above with reference to ​ and ​The described. Thus, it should be noted that embodiments of the method can be implemented using existing computer processors, or a special purpose computer processor incorporated for this or another purpose for a suitable system, or a hard-wired system. Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium (whether now known or later developed) that is suitable for carrying or storing desired program code means in the form of machine-executable instructions or data structures. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a machine, the machine properly views the connection as a machine-readable medium. Thus, any such connection is properly termed a machine-readable medium. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions comprise, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions. While example embodiments of the ICE system include a control unit as an integral part thereof, it can also be that the control unit can be a separate component of the vehicle, and / or arranged remotely from the system and in communication therewith.

[0101] The control unit can comprise a microprocessor, microcontroller, programmable digital signal processor or another programmable device. Thus, the control unit typically comprises electronic circuitry and connections and processing circuitry such that the control unit can communicate with different parts of the ICE system, such as the ICE, the ignition improver device, the fuel injector and the ignition source, or with any other components of the vehicle, such as the clutch, the gearbox, and / or any other parts required to operate in order to provide the functionality of the example embodiments. Typically, the control unit can also be configured to communicate with other parts of the vehicle, such as the brakes, the suspension and electrical auxiliary devices, such as the air conditioning system, in order to operate the vehicle as required by the driver. The control unit can comprise modules in the form of hardware or software, or partly in the form of hardware or software, and communicate using known transmission buses, such as a CAN bus, and / or wireless communication capabilities. The processing circuitry can be a general purpose processor or a special purpose processor. The control unit typically comprises non-transitory memory for storing computer program code and data thereon. Thus, the control unit can be implemented in many different configurations.

[0102] The control unit 90 can be or include any number of hardware components for data or signal processing or for executing computer code stored in a memory. The memory can be one or more devices for storing data and / or computer code for completing or facilitating the various methods described in the specification. The memory can include volatile or non-volatile memory. The memory can include a database component, a rule- based component, a script component, or any other type of information storage structure for supporting the various activities of the specification. According to an exemplary embodiment, any distributed or local memory device can be utilized with the systems and methods of the specification. According to an exemplary embodiment, the memory is communicably connected to the processor (e.g., via a circuit or any other wired, wireless, or network connection) and includes computer code for executing one or more processes described herein.

[0103] Also, while a particular order of method steps can be shown in the figures, the order of steps can differ from what is depicted. Additionally, two or more steps can be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule-based logic and other logic to accomplish various connection steps, processing steps, comparison steps, and decision steps.

[0104] It should be understood that the present disclosure is not limited to the embodiments described above and shown in the drawings; rather, persons skilled in the art will recognize that many modifications and variations are possible without departing from the scope of the present claims. As an example, the low cetane fuel is any one of hydrogen gas, hydrol, methanol, and ammonia. Additionally, the ignition source for operating the ICE in SI mode is any one of a spark plug, a glow plug, and a pilot fuel injection.

Claims

1. A single fuel internal combustion engine system (10) for a vehicle, comprising: An internal combustion engine (ICE) (20) capable of operating on a low-cetane fuel (32), the low-cetane fuel being any one of hydrogen, methanol, ammonia, E85, pure ethanol, and naphtha, the internal combustion engine having a cylinder (14) at least partially defining a combustion chamber and an ignition source (17) for the low-cetane fuel; a fuel injector (30) for injecting the low cetane fuel into the combustion chamber; an ignition improver device (40) in fluid communication with the fuel injector and further configured to supply an ignition improver fluid to the low cetane fuel; a control unit (90) configured to cause the ICE to selectively operate in a spark ignition (SI) mode and a compression ignition (CI) mode, The control unit is configured to determine an ICE operating condition and control the ignition improver device to supply a given amount of ignition improver fluid to the low cetane fuel based on the determined ICE operating condition.

2. The system according to claim 1, wherein: The control unit is configured to, in response to receiving a control signal indicating switching from the SI mode to the CI mode, control the ignition improver device to supply the given amount of ignition improver fluid to the low cetane number fuel, such that the ignition improver fluid is supplied to the low cetane number fuel during the switching from the SI mode to the CI mode.

3. The system according to claim 1 or 2, wherein: The ignition improver fluid is supplied to the low cetane fuel at a location in a fluid conduit disposed upstream of the fuel injector.

4. The system according to claim 1 or 2, wherein: The fuel injector is adapted to receive the low cetane fuel and the ignition improver fluid via separate first and second inlets such that the low cetane fuel and the ignition improver fluid mix at the fuel injector.

5. The system according to claim 1 or 2, wherein: The fuel injector is adapted to supply a mixed amount of low cetane fuel and an ignition improver fluid to the combustion chamber via a common outlet.

6. The system according to claim 1 or 2, wherein: The control unit is configured to determine the given amount of ignition improver fluid based on the magnitude of the determined ICE operating condition.

7. The system according to claim 1 or 2, wherein: The control unit is configured to increase the amount of ignition improver fluid if the determined ICE operating conditions correspond to non-favorable auto-ignition ICE conditions, and / or wherein, The control unit is configured to reduce the amount of the ignition improver fluid if the determined ICE operating conditions correspond to favorable auto-ignition ICE conditions.

8. The system according to claim 1 or 2, wherein: The ICE operating condition indicates any one of an ICE load, an ICE speed value, a cylinder pressure level, and a temperature level.

9. The system according to claim 1 or 2, wherein: The ignition improver fluid comprises a liquid or gas containing a substance that affects the auto-ignition temperature of the low cetane fuel.

10. The system according to claim 9, wherein: The substance of the ignition improver fluid includes any one of nitrates, nitroalkanes, nitrocarbonates, and peroxides.

11. The system according to claim 1 or 2, wherein: The ignition source for operating the ICE in the SI mode is any one of a spark plug, a glow plug, and pilot fuel injection.

12. A method (100) for controlling a single fuel internal combustion engine system (10) of a vehicle, the system comprising: An internal combustion engine (ICE) (20) capable of operating on a low-cetane fuel, the low-cetane fuel being any one of hydrogen, methanol, ammonia, E85, pure ethanol, and naphtha, and comprising a cylinder at least partially defining a combustion chamber and an ignition source for the low-cetane fuel; and a fuel injector for injecting the low-cetane fuel into the combustion chamber. an ignition improver device (40) in fluid communication with the fuel injector for supplying an ignition improver fluid to the low cetane fuel, the method comprising: operating the ICE in a spark ignition SI mode ( S10 ); determining ( S20 ) ICE operating conditions; and Based on the determined ICE operating conditions, a given amount of ignition improver fluid is supplied (S30) to the low cetane fuel.

13. The method of claim 12, further comprising switching (S40) from the SI mode to a compression ignition CI mode.

14. The method according to claim 12 or 13, further comprising: If the determined ICE operating conditions correspond to non-favorable auto-ignition ICE conditions, increasing the amount of ignition improver fluid, and / or further comprising: if the determined ICE operating conditions correspond to favorable auto-ignition ICE conditions, decreasing the amount of ignition improver fluid.

15. The method according to claim 12 or 13, further comprising: The fuel injector is controlled to supply a mixed low cetane fuel and ignition improver fluid to the combustion chamber of the cylinder.

16. The method according to claim 12 or 13, further comprising: Based on the determined ICE operating conditions, different cylinders are operated in different modes.

17. A vehicle comprising an internal combustion engine system according to any one of claims 1 to 11.

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