Method for calculating a fuel temperature in an injection system of an internal combustion engine with multiple cylinder banks, computing unit and computer program

Abstract

The present invention relates to a method for calculating a fuel temperature in an injection system of an internal combustion engine with multiple cylinder banks, comprising measuring a fuel temperature in one or more components (118, 218, 115, 215, 112, 212, 119, 219, 114, 214) of the injection system at each cylinder bank (101, 201) of the internal combustion engine to create a fuel temperature model; determining a number of sub-models for the fuel temperature model depending on the measured fuel temperature; parameterizing the determined sub-models depending on the measured fuel temperature; and calculating a fuel temperature in the injection system using the parameterized sub-models.

Description

[0001] The present invention relates to a method for calculating the fuel temperature in an injection system of an internal combustion engine with multiple cylinder banks, a computing unit and a computer program for carrying it out. Background of the invention

[0002] For many functions controlling an injection system in an internal combustion engine, it is advantageous to know the fuel temperature in the high-pressure section of the injection system in order to compensate for temperature effects that influence the amount of fuel injected. Since the fuel temperature at this point in the injection system is difficult to measure, modern engine control units may instead include functions that calculate the fuel temperature in the high-pressure section of the injection system.

[0003] In this context, DE 10 2007 053 082 A1 discloses a method for determining the fuel temperature of a common-rail fuel injection system, in which an energy balance model is used that calculates the fuel temperature at several points in the high-pressure section of the injection system based on a fuel temperature measured in the low-pressure section. The subject matter of this publication is hereby incorporated into this application by reference.

[0004] However, the method described in DE 10 2007 053 082 A1 is based on investigations on inline engines and is only conditionally suitable for internal combustion engines with multiple cylinder banks, such as V and / or W engines. In these engines, the fuel temperatures of the individual cylinder banks can differ significantly, for example, due to different fuel routing and / or different temperatures in the engine compartment. Disclosure of the invention

[0005] According to the invention, a method for calculating a fuel temperature in an injection system of an internal combustion engine with multiple cylinder banks, particularly when a cylinder configuration deviates from that of an inline engine (for example, in V-engines, boxer engines, or W-engines), a computing unit, and a computer program for carrying out this calculation, comprising the features of the independent claims, are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

[0006] The internal combustion engine can be, in particular, a diesel engine, and the injection system can be a so-called common-rail system. The injection system can be connected to a fuel tank and, for example, include a pressure generator, such as a high-pressure pump, and a high-pressure accumulator for each cylinder bank of the internal combustion engine. At least one injector can be connected to the high-pressure accumulator of each cylinder bank, which can inject fuel into the internal combustion engine. A low-pressure section of the injection system can extend, for example, from the fuel tank to the pressure generators of the individual cylinder banks. A temperature sensor can be located in the low-pressure section, for example, in an inlet to the pressure generators, which measures the fuel temperature during operation of the internal combustion engine. A high-pressure section of the injection system can extend, for example,according to the number of cylinder banks of the internal combustion engine, divide into several partial high-pressure areas, each extending from the high-pressure pump to at least one injector in the high-pressure accumulator of the respective cylinder bank.

[0007] The invention enables the highly accurate calculation of fuel temperature in different components of the partial high-pressure sections of the injection system. For this purpose, a fuel temperature in the low-pressure section of the injection system can be measured using a temperature sensor, and the fuel temperature in the individual components of the partial high-pressure sections can be calculated based on the measured fuel temperature using an energy balance in each component.

[0008] In the method according to the invention, a fuel temperature model is first created by measuring the fuel temperature in one or more components of the injection system at each cylinder bank of the internal combustion engine. The one or more components can advantageously be components in the individual partial high-pressure sections of the injection system, in which the fuel temperature is subsequently to be calculated by the fuel temperature model using the energy balance. In particular, the fuel temperature can be measured in the high-pressure pump, in the connection or line from the high-pressure pump to the high-pressure accumulator (also referred to as the high-pressure line), in the high-pressure accumulator, in the connection or line from the high-pressure accumulator to the at least one injector (also referred to as the injector line), and in the injector of each partial high-pressure system. For this purpose, temperature sensors, e.g., [further details omitted], can be installed on or in the individual components.Thermocouples must be positioned in such a way that they accurately measure the fuel temperature inside the component. Other suitable temperature measuring devices can also be used instead of thermocouples. This allows, for example, the determination of whether the fuel temperatures differ between identical components on the different cylinder banks of the internal combustion engine.

[0009] Depending on the measured fuel temperatures, a number of sub-models for the fuel temperature model are then determined. A sub-model can be specifically configured to calculate an energy balance in a particular component of a partial high-pressure system and to determine the fuel temperature within that component. A sub-model for calculating the fuel temperature in a partial high-pressure system is developed based on specific conditions and physical processes within the system to enable a more accurate prediction of the fuel temperature. For example, a sub-model can be determined for each component of the high-pressure system, such as the pressure generator, the high-pressure line from the pressure generator to the high-pressure accumulator, the high-pressure accumulator, the injector line from the high-pressure accumulator to the at least one injector, and the at least one injector itself.If a large number of injectors are present in the injection system, a sub-model can be determined for each injector and each injector line between the high-pressure accumulator and the injector.

[0010] For this purpose, the following equation (1) can be used, for example: m cpdTKSBTdt=m˙ cp(TKSein−TKSBT)−αA(TKSBT−TBT)

[0011] This presents m cpdTKSBTdt represents a change in the fuel heat energy in a component, where m is a fuel mass in the component, c p the heat storage capacity of the fuel and T KSBT to describe the temperature of the fuel in the component.

[0012] This temperature results from the difference between the supplied and removed fuel heat energy ṁ c p (T KSein - T KSBT ) minus a heat transfer αA(T KSBT - T BT ) on the component, where T KSeinan inlet temperature of the fuel into the component, α the heat transfer coefficient from the fuel to the component, A a heat transfer area and T BT to describe a component temperature.

[0013] Equation (1) represents the simplest case of a sub-model, which can be used, for example, to calculate the fuel temperature in the line from the high-pressure pump to the high-pressure accumulator, the fuel temperature in the high-pressure accumulator, and the fuel temperature in the injector line from the high-pressure accumulator to at least one injector. Additional heat sources, such as an electrically actuated pressure regulating valve, may also be included in the calculation of the fuel temperature in the high-pressure accumulator.

[0014] Furthermore, in the sub-models for the high-pressure pump and the injector, a temperature change due to compression or expansion of the fuel must also be taken into account.

[0015] Furthermore, each sub-model contains additional energy balance equations for determining the individual component temperatures T. BT This requires models that essentially account for heat transfer by thermal radiation and convection from the fuel to the component, as well as from the component to its surroundings or adjacent components. The individual equations of the sub-models can be formulated in a system of differential equations and solved analytically or numerically.

[0016] According to one embodiment, to determine the number of sub-models, a measured fuel temperature in identical components on different cylinder banks can be compared, and depending on a fuel temperature difference between the identical components, an individual sub-model for each of the identical components or a group sub-model for the identical components on the different cylinder banks can be determined or used.

[0017] If, for example, in a V-engine, the fuel temperature in a first high-pressure accumulator on the first cylinder bank of the engine differs only slightly from that in a second high-pressure accumulator on the second cylinder bank, a group sub-model can be determined for the high-pressure accumulator that can be used for the partial high-pressure systems of both cylinder banks. In other words, the fuel temperature in the high-pressure accumulator can be determined in this case as if there were a single, shared high-pressure accumulator. However, model parameters, such as the heat transfer coefficient a and / or the heat transfer area A of the sub-models assigned to the respective partial high-pressure systems, can be adjusted to compensate for the slight differences in the fuel temperature of the two high-pressure accumulators.

[0018] However, if the measured fuel temperatures in the first and second high-pressure storage tanks differ significantly, a separate sub-model can be determined or used for each high-pressure storage tank.

[0019] According to one embodiment, a single submodel for identical components can always be determined or used when the fuel temperature difference between the same components on different cylinder banks is greater than a predetermined temperature difference threshold. The predetermined temperature difference threshold can, for example, be in a range of 5 K to 30 K, particularly 10 K. If the fuel temperature difference is less than or equal to the predetermined temperature difference threshold, a group submodel can be created.

[0020] To provide a single sub-model for each of the identical components on the different cylinder banks, equation (1) can be adapted as follows, for example. m1 cpdTKSBT1dt=m˙1 cp(TKSein1−TKSBT1)−αA(TKSBT1−TBT1) m2 cpdTKSBT2dt=m˙2 cp(TKSein2−TKSBT2)−αA(TKSBT2−TBT2)

[0021] It becomes clear that different fuel temperatures T KSBT1 , T KSBT2 in two identical components on different cylinder banks, e.g., due to different fuel inlet temperatures T KSein1' T KSein2 These differences can arise, for example, from varying heat inputs into the fuel in preceding components of the partial high-pressure system. Furthermore, different component temperatures (T) can also contribute. BT1 , T BT2 for the different fuel temperatures T KSBT1 , T KSBT2These differences could be due, for example, to different positions of the components in the engine compartment. Such differences can be determined using individual sub-models and a system of differential equations that incorporates all the sub-models and can thus determine the fuel temperature in the individual components based on the measured fuel temperature.

[0022] Once a number of submodels for the fuel temperature model have been determined and the system of differential equations established, these submodels are parameterized based on the measured fuel temperature. The model parameters, such as the heat transfer coefficient α and / or the heat transfer area A, are advantageously defined such that the fuel temperature model calculates the measured fuel temperatures as accurately as possible. The number of submodels affects the number of model parameters, as a larger number of submodels necessitates a larger number of model parameters. For example, in individual submodels for identical components on different cylinder banks, the same model parameters can be assigned different values ​​to represent the measured differences in fuel temperature.

[0023] In addition to the fuel temperature, it is advantageous to measure the component temperature of one or more components of the injection system on each cylinder bank of the internal combustion engine. Specifically, the component temperature can be measured on all components where the fuel temperature has been measured. For this purpose, temperature sensors, such as thermocouples, can be attached to the respective components in such a way that they accurately record their component temperatures. Alternatively, other suitable temperature measuring devices can be used. This allows, for example, the determination of whether component temperatures of identical components differ on the various cylinder banks of the internal combustion engine.In particular, the measured component temperatures can also be used to parameterize the fuel temperature model and the model parameters of the individual sub-models can be adjusted so that the fuel temperature model calculates the measured component temperatures as accurately as possible.

[0024] Once all submodels of the fuel temperature model are parameterized, the fuel temperature in the injection system is calculated using these parameterized submodels. Specifically, the fuel temperature can be calculated in each component of the partial high-pressure systems for which a submodel (group or individual submodel) exists.

[0025] According to one embodiment, the fuel temperature in each of the one or more components can be calculated as a function of the fuel mass flow through the component.

[0026] For this purpose, equations (1) to (3) can be used, for example, to calculate an energy balance in a component of the partial high-pressure systems. Equation (1) can be used to calculate a group sub-model, and equations (2) and (3) can be used to calculate two individual sub-models. In these equations, a difference between the supplied and discharged fuel heat energy ṁ c is used. p (T KSein - T KSBT ) present, which is significantly influenced by the fuel mass flow through the component. In group sub-models, a total fuel mass flow ṁ through the same components can be considered, while in individual sub-models for identical components, the fuel mass flow ṁ can be distributed among them (ṁ1, ṁ2 ....).

[0027] In particular, the fuel mass flow rate ṁ can be divided equally among the individual sub-models, such that, for example, ṁ1 = ṁ2. In special cases, such as cylinder deactivation, the fuel mass flow rate can be adjusted accordingly by the individual sub-models.

[0028] According to one embodiment, the fuel temperature in each of the one or more components can be calculated depending on its component temperature.

[0029] For this purpose, equations (1) to (3) can be used, for example, in which a term αA(T) KSBT - T BT The equation includes a calculation that takes into account heat transfer from the fuel to the component. It becomes clear that as the component temperature decreases, the heat transfer increases, and thus, according to equations (1) to (3), the fuel temperature in the component decreases.

[0030] According to one embodiment, the fuel temperature in each of the one or more components can be calculated as a function of a temperature in the combustion engine's environment. This temperature influences heat transfer from a component to its environment and thus the component temperature as well as the fuel temperature within the component (see above). In particular, the combustion engine's environment can be an engine compartment in a vehicle.

[0031] According to one embodiment, the temperature in the vicinity of the internal combustion engine can be calculated using an ambient temperature model. This model can, in particular, calculate the temperature in the engine compartment of a vehicle as a function of the outside air temperature, the cooling capacity of the engine radiator, and any radiator shutters, as described in DE 10 2017 215 257 A1. The engine compartment temperature model described therein also includes several sub-models, such as a cylinder head temperature model, an intercooler temperature model, and an air conditioning condenser model. The subject matter of this publication is hereby incorporated into this application by reference.

[0032] When using an internal combustion engine with multiple cylinder banks, its attachments, such as exhaust gas turbochargers with charge air coolers or exhaust aftertreatment components, can be arranged asymmetrically in the engine compartment, which means that, for example, the engine compartment temperature in the vicinity of a first cylinder bank may have a different value than in the vicinity of a second cylinder bank.

[0033] According to one embodiment, an ambient temperature can be measured at at least two locations in the vicinity of the internal combustion engine, particularly in the engine compartment, and the ambient temperature model can be adapted based on the measured ambient or engine compartment temperature. Specifically, the engine compartment temperature can be measured in the vicinity of the first and second cylinder banks of the engine, and the ambient temperature model can be adapted if the difference between the two measured temperatures exceeds a predetermined temperature threshold. To adapt the ambient temperature model, individual sub-models, e.g., for the cylinder head model and / or the charge air cooler model, can be created, analogous to the fuel temperature model. In particular, a cylinder head model and an charge air cooler model can be created for each cylinder bank of the internal combustion engine and parameterized bank-specifically.

[0034] A computing unit according to the invention, e.g. an engine control unit of the internal combustion engine, is, in particular in terms of programming, equipped to carry out a method according to the invention as described above.

[0035] Implementing a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is also advantageous, as this incurs particularly low costs, especially if an executing engine control unit is already used for other tasks and is therefore already available. Finally, a machine-readable storage medium is provided with a computer program stored on it as described above. Suitable storage media or data carriers for providing the computer program are, in particular, magnetic, optical, and electrical storage media, such as hard drives, flash memory, EEPROMs, DVDs, etc. Downloading a program via computer networks (Internet, intranet, etc.) is also possible. Such a download can be wired or wireless (e.g., via a WLAN network, a 3G, 4G, 5G, or 6G connection, etc.).

[0036] Further advantages and embodiments of the invention will become apparent from the description of the accompanying drawings.

[0037] The invention is schematically illustrated with reference to exemplary embodiments in the drawings and is described below with reference to the drawings. Identical elements are designated with the same reference numerals and are therefore not described more than once unless necessary. Brief description of the drawings Fig. Figure 1 schematically shows an injection system with two partial high-pressure systems that can be operated using the method according to the invention. Fig. Figure 2 shows a flowchart with process steps of a method according to an embodiment of the invention. embodiment(s) of the invention

[0038] In Fig. Figure 1 schematically depicts an injection system with two partial high-pressure systems 100, 200, which can be operated using the method according to the invention. The injection system includes a low-pressure system, which in this case essentially comprises a fuel tank 300, to which the first and second partial high-pressure systems 100, 200 are each connected by means of a line not shown in detail. The first partial high-pressure system comprises a first pressure generator, which in this case is designed as a high-pressure pump 118, a first high-pressure accumulator 112, a first high-pressure line 115 between the first high-pressure pump 118 and the first high-pressure accumulator 112, and three first injectors 114, each of which is connected to the first high-pressure accumulator 112 by means of a first injector line 119. The three first injectors 114 each inject fuel into one cylinder 122 of a first cylinder bank 101 of an internal combustion engine not shown in detail.Excess fuel from the first injectors 114 and the first high-pressure accumulator 112 is returned to tank 300 via a first return line 116. A first temperature sensor 117 is installed in an unspecified line between tank 300 and the first high-pressure pump 118, which measures the fuel temperature in the supply line to the first high-pressure pump 118.

[0039] The second partial high-pressure system 200 is constructed according to the first partial high-pressure system and includes a second high-pressure pump 218, a second high-pressure accumulator 212, a second high-pressure line 215 between the second high-pressure pump 218 and the second high-pressure accumulator 212, and three second injectors 214, each connected to the second high-pressure accumulator 118 by a second injector line 219. The three second injectors 214 each inject fuel into one cylinder 222 of a second cylinder bank 201 of the internal combustion engine. Excess fuel from the second injectors 214 and the second high-pressure accumulator 212 is returned to the tank 300 via a second return line 216. A second temperature sensor 217 is installed in a line (not specified) between the tank 300 and the second high-pressure pump 218, which measures the fuel temperature in the supply line to the second high-pressure pump 218.

[0040] To determine the fuel temperature in the first and second part of the high-pressure system, a fuel temperature model can be created for each, which includes sub-models for the high-pressure pump 118 or 218, the high-pressure line 115 or 215 from the high-pressure pump 118 or 218 to the high-pressure accumulator 112 or 212, the high-pressure accumulator 112 or 212, the injector line 119 or 219 from the high-pressure accumulator 112 or 212 to the injectors 114 or 214, and the injectors 114 or 214.

[0041] To create the fuel temperature model, the fuel temperature can first be measured in the individual components 118 / 218, 115 / 215, 112 / 212, 119 / 219, and 114 / 214. These components can be equipped with suitable temperature measuring devices for this purpose. Depending on the measured fuel temperature, a number of sub-models for the fuel temperature model can then be determined, and each sub-model can be parameterized. Each sub-model can contain an energy balance equation, for example, according to equations (1) to (3). The model parameters of the sub-models or the energy balance equations can be chosen such that the fuel temperature model calculates the measured fuel temperatures as accurately as possible. The individual equations of the sub-models can be formulated in a system of differential equations and solved analytically or numerically.The fuel temperature model can receive as an input a fuel temperature measured by the temperature sensors 117 and 217 in the inlet of the two high-pressure pumps 118 and 218, respectively.

[0042] For each component 118, 218, 115, 215, 112, 212, 119, 219, 114, and 214, an individual sub-model can be created, or for identical components 118 or 218, 115 or 215, 112 or 212, 119 or 219, and 114 or 214 in the two partial high-pressure systems 100 and 200, respectively, a group sub-model can be created. In particular, an individual sub-model for identical components can always be created if the fuel temperature difference between the identical components in the two partial high-pressure systems 100 and 200 is greater than a predetermined temperature difference threshold. The predetermined temperature difference threshold can, for example, be in a range of 5 K to 30 K, specifically 10 K. If the fuel temperature difference is less than or equal to the predetermined temperature difference threshold, a group sub-model can be created.

[0043] Fig. Figure 2 shows a flowchart with process steps of a method according to an embodiment of the invention. After starting the method in step 500, a fuel temperature is first measured in each of the components 118, 218, 115, 215, 112, 212, 119, 219, 114 and 214 of the [unclear text]. Fig. The fuel temperatures of the injection system shown in Figure 1, with two partial high-pressure systems 100 and 200, are measured (step 501). Subsequently, in step 502, the fuel temperatures in identical components 118 and 218, 115 and 215, 112 and 212, 119 and 219, and 114 and 214 are compared. For example, a fuel temperature measured in the first high-pressure pump 118 is compared with a fuel temperature measured in the second high-pressure pump 218. Similarly, a measured fuel temperature in the first high-pressure accumulator 112 is compared with a measured fuel temperature in the second high-pressure accumulator 212, and so on.

[0044] If a fuel temperature difference between identical components in the two partial high-pressure systems is greater than a predetermined temperature difference threshold (path "1"), a single submodel is created in step 503; otherwise (path "0"), a group submodel is created in step 504. This determines the number of submodels in the fuel temperature model. The created submodels are parameterized in step 505 depending on the measured fuel temperature, and in step 506, a fuel temperature in the components of the two partial high-pressure systems 100 and 200 is calculated using the parameterized submodels. The procedure is terminated in step 507. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2007 053 082 A1 [0003, 0004] DE 10 2017 215 257 A1

[0031]

Claims

[1] Method for calculating a fuel temperature in an injection system of an internal combustion engine with multiple cylinder banks, comprising the steps: - Measuring (501) a fuel temperature in one or more components (118, 218, 115, 215, 112, 212, 119, 219, 114, 214) of the injection system on each cylinder bank (101, 201) of the internal combustion engine to create a fuel temperature model; - Determine (503, 504) a number of submodels for the fuel temperature model depending on the measured fuel temperature; - Parameterizing (505) the selected submodels as a function of the measured fuel temperature; and - Calculating (506) a fuel temperature in the injection system using the parameterized submodels. [2] Method according to claim 1, wherein to determine the number of sub-models a fuel temperature in identical components (118, 218; 115, 215; 112, 212; 119, 219; 114, 214) on different cylinder banks is compared and depending on a fuel temperature difference a single sub-model for each of the identical components or a group sub-model for the identical components on the different cylinder banks is determined (502). [3] Method according to claim 2, wherein a single sub-model for the same components (118, 218; 115, 215; 112, 212; 119, 219; 114, 214) on different cylinder banks (101, 201) is determined when the fuel temperature difference between these is greater than a predetermined temperature difference threshold (503), and a group sub-model for these is determined when the fuel temperature difference is less than the predetermined temperature difference threshold (504). [4] Method according to one of the preceding claims, wherein the calculation of the fuel temperature in each of the one or more components (118, 218, 115, 215, 112, 212, 119, 219, 114, 214) is carried out as a function of a fuel mass flow through the component (118, 218, 115, 215, 112, 212, 119, 219, 114, 214). [5] Method according to one of the preceding claims, wherein the calculation of the fuel temperature in each of the one or more components (118, 218, 115, 215, 112, 212, 119, 219, 114, 214) is carried out as a function of its component temperature. [6] Method according to one of the preceding claims, wherein the calculation of the fuel temperature in each of the one or more components (118, 218, 115, 215, 112, 212, 119, 219, 114, 214) is carried out as a function of a temperature in an environment of the internal combustion engine. [7] Method according to claim 6, wherein the temperature in the vicinity of the internal combustion engine is calculated using an ambient temperature model. [8] Method according to claim 6 or 7, wherein the temperature is measured at at least two positions in the environment of the internal combustion engine and the ambient temperature model is adapted depending on the at least two temperatures. [9] Computing unit configured to perform all process steps of a process according to any of the preceding claims. [10] Injection system of an internal combustion engine with multiple cylinder banks, comprising: one or more components (118, 218, 115, 215, 112, 212, 119, 219, 114, 214), at least one sensor (117) for measuring the fuel temperature in the one or more components (118, 218, 115, 215, 112, 212, 119, 219, 114, 214), the computing unit according to claim 9. [11] Computer program that causes a computing unit, in particular the injection system according to claim 10, to carry out all process steps of a method according to any one of claims 1 to 8 when executed on the computing unit. [12] Machine-readable storage medium with a computer program stored thereon according to claim 11.

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