Method for operating a fuel-operated internal combustion engine system, and control device for carrying out said method

Abstract

A method for operating a fuel-operated internal combustion engine system which has a combustion chamber (2) in which a fuel / air mixture is burned, wherein the method comprises: a) determining the combustion energy as the energy released upon combustion of the fuel, and the heat capacity of an inert portion as the heat capacity of at least part of an inert portion of the contents of a combustion chamber, and b) controlling and / or regulating and / or outputting at least one parameter of the internal combustion engine system on the basis of the determined combustion energy and the determined heat capacity.

Description

[0001] Method for operating a fuel-powered

[0002] Internal combustion engine system and control device for carrying out the method

[0003] The present invention relates to a method for operating an internal combustion engine system operated with fuel, preferably hydrogen, and to a control device for carrying out the control method.

[0004] For example, EP 1 754 874 A1 discloses an internal combustion engine that uses hydrogen as fuel. The fuel quantity is determined in accordance with a fuel-air ratio (combustion lambda) and based on the exhaust gas recirculation (EGR) flow rate. The internal combustion engine is thus controlled based on the two parameters, combustion lambda and the EGR flow rate.

[0005] However, this method has the disadvantage that, due to the variation in combustion lambda depending on the amount of exhaust gas recirculation, different combustion chamber components and their interrelationships can occur in the combustion chamber of the internal combustion engine. This complicates a thermodynamic analysis of the conditions in the combustion chamber. Another problem is that thermodynamic considerations are ignored when setting the ignition timing.

[0006] It is therefore an object of the invention to provide an improved method for operating an internal combustion engine system which is particularly suitable for fuels without a predetermined combustion lambda.

[0007] This object is achieved according to the invention by a method according to claim 1.

[0008] According to a first aspect, there is provided a method for operating an internal combustion engine system which is operated with fuel, preferably hydrogen, and which has a combustion chamber in which a fuel-air mixture is combusted, the method comprising: a) determining a combustion energy as an energy released with the combustion of the fuel, and an inert component heat capacity as a heat capacity of at least a part of an inert component of a combustion chamber content, and b) determining and / or controlling and / or regulating and / or outputting at least one parameter of the internal combustion engine system based on the determined combustion energy and the determined heat capacity.

[0009] According to this aspect, a thermodynamic state in the combustion chamber can be taken into account by determining the combustion energy and the inert component heat capacity. In particular, the heat energy released during combustion can be related to the components of the combustion chamber that are to be heated but not participating in the combustion. This allows the control and regulation in b) to be improved. It should be noted that the term "determine" means that the combustion energy and the inert component heat capacity are determined at least implicitly, preferably explicitly. Sensor measurements can be used, or the said variables can be calculated numerically and / or analytically. "Determine" means, in particular, setting the parameter. "Control" means, in particular, achieving the specified parameter, at least within certain limits, by adjusting at least one manipulated variable.In contrast to open-loop control, the term "control" refers to feedback of the variable to be controlled. "Control" can also mean precise feedforward control, where the parameter is set a priori to determine the corresponding manipulated variable and obtain the precise controlled variable.

[0010] It is also possible to output at least one parameter to a user based on a). This could, for example, be the combustion energy and heat capacity directly, or a combustion temperature specified further down.

[0011] The parameter can be a parameter of a process or device. It can be a parameter related to the combustion chamber or a parameter related to a device downstream of the combustion chamber, such as an exhaust aftertreatment system.

[0012] The fuel used is preferably a fuel without a predetermined combustion lambda, such as hydrogen. With such a fuel, fluctuating combustion chamber volumes may occur, which influence the control and / or regulation according to b).

[0013] Preferably, b) is performed exclusively on the basis of a). Thus, combustion lambda or EGR flow do not need to be determined.

[0014] Preferably, the combustion energy is determined based on a calorific value of the fuel.

[0015] Thus, the combustion energy can be reliably determined based on an easily accessible value.

[0016] Preferably, the inert fraction heat capacity is determined based on at least a portion of a mass fraction of the inert fraction.

[0017] By determining the mass fraction, the inert fraction heat capacity can be determined with high accuracy.

[0018] Preferably, the inert fraction heat capacity is determined based on the composition of the inert fraction. This allows the inert fraction heat capacity to be determined with high accuracy with regard to the components of the inert fraction. The conditions prevailing in the combustion chamber can be taken into account.

[0019] In particular, the inert fraction heat capacity is preferably determined based on component-specific heat capacities of components of the composition.

[0020] As a result, the inert component heat capacity can be determined with high accuracy, since the respective specific heat capacity of the components is taken into account for determining it, and the control and / or regulation according to b) can still be carried out reliably.

[0021] Furthermore, a specific heat capacity, in particular at least a component-specific heat capacity, can be determined based on reference data, further in particular based on NASA polynomials.

[0022] This reduces the effort required for sensor-based determination. The reference data can be stored in a memory device whose memory can be read.

[0023] According to another aspect, a combustion temperature can be determined based on a ratio of combustion energy and inert fraction heat capacity, and b) carried out based on the determined combustion temperature.

[0024] According to this aspect, a thermodynamic state variable can be determined that adequately describes the state in the combustion chamber, and the control and / or regulation according to b) can be simplified. In particular, b) does not have to be based on the combustion lambda and / or the EGR quantity. The combustion temperature can, in particular, be a combustion temperature averaged across the combustion chamber. This represents an advantage over sensors that can only measure a local temperature. Sensors for measuring the combustion temperature can even be omitted entirely or provided additionally for monitoring purposes.

[0025] Preferably, to determine the combustion temperature, a final compression temperature is also determined, which is a temperature at maximum compression of the fuel-air mixture.

[0026] Thus, the influence of compression in the combustion chamber on the resulting combustion temperature can be considered in isolation. The final compression temperature, in particular, is a temperature that only considers compression and does not take combustion into account, which influences the combustion temperature via the aforementioned ratio of combustion energy to inert heat capacity.

[0027] Alternatively or additionally, the at least one parameter may include or be the combustion temperature.

[0028] Thus, the combustion temperature can be determined, controlled, and / or regulated. The combustion temperature can be determined as described above and thus fed back into the control loop. The feedback can also be a priori, i.e., in the sense of feedforward control.

[0029] Preferably, a comparison can be carried out between the determined combustion temperature and a permissible combustion temperature range, and when the permissible combustion temperature range is left, an ignition point for the combustion chamber and / or a fuel quantity and / or an air quantity and / or an exhaust gas recirculation quantity and / or an inert agent supply quantity can be adjusted.

[0030] This allows for appropriate response to a non-permissible combustion temperature. The permissible combustion temperature range can be determined, for example, based on permissible emissions and / or a maximum exhaust gas temperature and / or a minimum exhaust gas temperature. "Adjustment" here specifically means that the respective parameter is the control variable. The adjustment can be made relative to a previous value or relative to a specified value. "Exiting" here specifically means a theoretical departure.

[0031] Preferably, the combustion temperature is additionally determined based on an ignition timing parameter.

[0032] This allows the influence of ignition timing to be taken into account. The ignition timing parameter can be a factor in determining the combustion temperature. It can be determined empirically, for example, on a test bench.

[0033] When an ignition timing limit is reached, a fuel quantity can be adjusted.

[0034] Thus, even in a case where adjustment of the ignition timing is no longer possible, a combustion temperature within the permissible combustion temperature range can be ensured, since the fuel quantity influences the combustion energy and thus the combustion energy can be adjusted accordingly.

[0035] Preferably, particularly preferably within the permissible combustion temperature range, the combustion temperature is controlled to a preset combustion temperature, in particular by adjusting an air flow and / or an exhaust gas recirculation flow and / or an inert agent supply flow into the combustion chamber. Thus, the combustion temperature can be controlled to a fixed value. This control can take place, in particular, with a substantially constant power requirement. In the control process, the air flow, the exhaust gas recirculation flow and / or the inert agent supply flow can be manipulated variables that influence the resulting combustion temperature. Here, "control" refers, in particular, to pre-control.

[0036] In the above control regarding the permissible combustion temperature range and / or the control on the combustion temperature, at least one of the ignition timing for the combustion chamber and / or a fuel amount and / or an air amount and / or an exhaust gas recirculation amount and / or an inert agent supply amount may be prioritized over at least one other of the ignition timing for the combustion chamber and / or a fuel amount and / or an air amount and / or an exhaust gas recirculation amount and / or an inert agent supply amount.

[0037] This means that the at least one other parameter can only be adjusted if an adjustment of the at least one parameter is no longer possible, especially in the current cycle. However, the at least one parameter is preferably adjusted in the following cycle.

[0038] For example, an adjustment of the fuel quantity can only be made when an adjustment of the exhaust gas recirculation quantity and / or the inert agent supply quantity and / or the air quantity is no longer possible.

[0039] Thus, the combustion temperature can be adequately controlled and / or regulated.

[0040] However, when controlling to a specific target combustion temperature, the fuel quantity in particular cannot be a control variable. Thus, the target fuel quantity can be supplied to the combustion chamber.

[0041] According to yet another aspect, the at least one parameter can be determined, controlled and / or regulated based on the combustion temperature and a knock signal value of the combustion chamber, in particular an amount thereof.

[0042] Thus, the determined combustion temperature can also be used to reduce knocking. An adjustment of the at least one parameter can be correlated with the combustion temperature and the knock signal value. In particular, the at least one parameter can be determined, controlled, and / or regulated such that an absolute value of the knock signal value decreases.

[0043] In particular, the at least one parameter can include or be the fuel quantity and / or the exhaust gas recirculation quantity and / or the inert agent supply quantity. Thus, knocking can be reduced by adjusting, in particular reducing, the fuel quantity in the current cycle or by increasing the exhaust gas recirculation quantity in the current or subsequent cycle. The inert agent supply quantity can also be increased in the current cycle.

[0044] It is advantageous if a fuel quantity is reduced based on the combustion temperature to reduce knocking, and a reduction in a preset fuel quantity is at least partially redistributed to at least one other combustion chamber. If redistribution is not possible, an exhaust gas recirculation quantity, an inert agent supply quantity, and / or an air quantity can be adjusted, and if adjustment of these quantities is not possible, the fuel quantity to the combustion chamber can be reduced.

[0045] In particular, a default combustion temperature is determined based on the knock signal value, and the at least one parameter is determined, controlled and / or regulated based on the default combustion temperature.

[0046] Thus, the knock signal value can be used to determine a desired target combustion temperature, which in turn can be used to determine / control / regulate the at least one parameter.

[0047] In particular, the target combustion temperature can be determined based on a difference from a reference combustion temperature.

[0048] According to this method, the target combustion temperature can be specifically reduced compared to a reference combustion temperature, which can correspond to a previously determined combustion temperature or a limit value of the permissible combustion temperature range, so that knocking in the combustion chamber can be reliably reduced.

[0049] Alternatively and / or additionally, the target combustion temperature may depend on the reference combustion temperature and / or the knock signal value.

[0050] This allows the target combustion temperature to be variable, so that it varies according to the reference combustion temperature and / or the knock signal value. Knock reduction can thus be achieved reliably. Excessive adjustment of at least one parameter can also be prevented.

[0051] According to a further aspect, which can be provided independently or dependently on the above aspects, a method is provided for operating an internal combustion engine system which is operated with fuel, preferably hydrogen, and has a combustion chamber in which a fuel-air mixture is combusted, the method comprising: determining a combustion duration from an ignition time to a predetermined time at which a predetermined combustion conversion rate is reached at which a predetermined portion of the fuel in the combustion chamber has been combusted, and determining an ignition time based on the determined combustion duration.

[0052] In the current state of the art, the ignition timing is adjusted based on engine maps, for example, engine speed and torque. However, no thermodynamic properties can be derived from this. In contrast, according to this aspect, when adjusting the ignition angle, the ignition timing is set based on a predetermined combustion conversion rate. This ensures that combustion proceeds as desired over time. This makes it possible to control the effects of the combustion conversion rate, such as nitrogen oxide emissions, knocking, combustion efficiency, and changes in combustion temperature.

[0053] Preferably, the predetermined combustion conversion rate is in a range of 30 to 70%, more preferably 40 to 60%, particularly preferably 50%.

[0054] The greatest combustion activity can occur in these value ranges, allowing the corresponding ignition timing to be determined for orderly combustion. Furthermore, this conversion rate varies relatively large depending on the composition of the combustion chamber contents, allowing the ignition timing to be determined with high accuracy.

[0055] Preferably, the combustion duration is determined based on the combustion temperature according to the above aspects.

[0056] Thus, the determination during operation of the internal combustion engine system can be easily determined based on the composition of the combustion chamber volume, specifically on a single parameter: the combustion temperature, which is determined from the combustion chamber volume. For example, characteristic maps can be generated in advance in simulation or on the test bench that represent the time until the combustion conversion rate is reached as a function of the combustion temperature.

[0057] Preferably, the predetermined time is predetermined based on a knock signal value of the combustion chamber, in particular if the knock signal value indicates stronger knocking, the predetermined time is shifted to a later time.

[0058] This allows for appropriate responses to knocking in the respective combustion chamber and for the knocking to be alleviated while keeping the thermodynamics of combustion under control.

[0059] A further aspect provides an electronic control device / program configured to carry out a method according to at least one of the preceding claims in an internal combustion engine system. A computer-readable storage medium on which the program is stored can also be provided.

[0060] Thus, the above aspects can be ensured in the internal combustion engine system by the control device.

[0061] The invention also relates to a vehicle having the control device and the internal combustion engine system, for example a truck.

[0062] The present invention is described in more detail below with reference to the accompanying figures.

[0063] They show:

[0064] Fig. 1 shows a cross-sectional view of an internal combustion engine system;

[0065] Fig. 2 is a flow chart to illustrate the control / regulation with regard to the combustion temperature.

[0066] Fig. 3 is a flow chart to illustrate the ignition timing determination.

[0067] Fig. 4 is a characteristic curve showing the combustion duration as a function of the combustion chamber volume.

[0068] Fig. 5 shows a modified flow chart of the control / regulation with regard to the combustion temperature.

[0069] Fig. 6 shows a flow chart for reducing knock based on combustion temperature.

[0070] Fig. 1 shows an example of an internal combustion engine system 1 to which the present invention can be applied. It should be noted that the following components of said system are not exhaustive, and individual components may be omitted and others added.

[0071] The internal combustion engine system 1 here is a hydrogen engine and is preferably operated exclusively with hydrogen. It has at least one combustion chamber 2 with a circular cross-section, which is formed in a cylinder 3 that delimits the combustion chamber 2 along its circumference. At the upper end, the combustion chamber 2 is delimited by a cylinder head 4 and at the lower end by a reciprocating piston 5 that moves in the axial direction of the cylinder 3. Furthermore, an inflow line 6 is provided through which ambient air flows into the combustion chamber 2. The fuel, in this case hydrogen, is also injected into the inflow line 6 via an injection nozzle 9. It should be noted that the external mixture formation is exemplary, and an internal mixture formation can also be carried out instead, wherein the injection nozzle is designed to inject directly into the combustion chamber 2.The air volume is not controllable in this case, but a throttle device can also be provided to control the air volume. A fuel tank 14 supplies the fuel to the injection nozzle 9.

[0072] A fuel-air mixture can flow through a valve-operated inlet 8a into the combustion chamber 2, where it is combusted under compression by the piston 5 and ignited by an ignition device 10. Engine 1 is therefore preferably a spark-ignition engine, but compression-ignition versions are also conceivable.

[0073] The combusted mixture flows as exhaust gas through a valve-operated outlet 8b into an exhaust system 11. Located in the exhaust system 11 is a catalyst device 12, which may comprise at least one of a nitrogen oxide storage catalyst and an SCR catalyst. The exhaust gas flows at least partially through the catalyst device 12.

[0074] Upstream of the catalytic converter device 12 is an external high-pressure exhaust gas recirculation device 13, via which exhaust gas can be recirculated into the intake system 6. Alternatively, low-pressure exhaust gas recirculation or internal exhaust gas recirculation are also possible. The high-pressure exhaust gas recirculation device 13 can preferably recirculate a variable amount of EGR. For this purpose, it can have an adjustment valve.

[0075] Alternatively or in addition to the high-pressure exhaust gas recirculation system 13, an inert agent supply system can be provided in the engine 1, which supplies an inert agent such as water, which does not participate in combustion, in particular directly, into the combustion chamber. The inert agent can, in particular, be such that it undergoes a phase transition, such as evaporation, during the combustion cycle. The inert agent can, in particular, be liquid.

[0076] A control unit (ECU) 15 is provided and is connected to various components of the engine 1 via signal communication (represented by dashed lines). The control unit 15 can be configured as a single physical unit or can comprise multiple physical units. It can comprise a memory device and a computing unit on which processes can be executed.

[0077] The control device 15, for example, controls the fuel tank 14 and the injection nozzle 9 to supply a desired amount of fuel. Furthermore, the control device 15 can receive signals, such as from a tachometer provided on a crankshaft 7 coupled to the piston 5.

[0078] Furthermore, the control device 15 determines according to the invention a combustion energy and an inert component heat capacity of the mixture to be burned in the combustion chamber 2.

[0079] In detail, the control device 15 determines a combustion temperature Vk according to formula (1), the respective units of the fraction being given on the right-hand side:

[0080] Where: mu is the fuel mass,

[0081] Hu is the lower calorific value, minertGas is the mass of the inert component in the combustion chamber, cpinertGas is the specific heat capacity of the inert component in the combustion chamber,

[0082] T £ the final compression temperature

[0083] T £ can be determined as:

[0084] These include:

[0085] Tsuction pipe The temperature in the inflow line 6,

[0086] £ the compression ratio,

[0087] K is the isentropic coefficient of the mixture in the combustion chamber

[0088] K can be determined as: t

[0089] ^P l Gemissh~^G&misch

[0090] (3)

[0091] Where: epMixture is the specific heat capacity of the mixture in the combustion chamber, and

[0092] R is the specific gas constant of the mixture

[0093] To determine the above values, various sensors can be arranged in the engine 1.

[0094] The fuel mass ITIK can be determined as the fuel quantity / fuel mass instructed by the control device 15. The calorific value Hu can be stored in a storage device, for example, that of the control device 15 for the respective fuel.

[0095] A total mass mces in the combustion chamber can be determined as the sum of the fuel mass m^, the air mass, for which an air mass meter is provided in the intake manifold 6, and the EGR quantity / mass recirculated via the high-pressure exhaust gas recirculation system 13. The latter can be instructed by the control device 15 or detected by a sensor.

[0096] A mass of the oxygen participating in the combustion mo2,verbr can be calculated, for example, by the control device 15. Based on the assumption of complete combustion, a ratio to the fuel mass can be used for the calculation.

[0097] It should be noted that the mass of the inert fraction minertGas in formula (1) can be expressed as the difference between the total mass in the combustion chamber mces, and the fuel mass mK and the mass of the oxygen participating in the combustion mo2,verbr.

[0098] The specific heat capacity cpinertGas of the inert component in the combustion chamber can be determined using the so-called NASA polynomials, which serve as reference data and can be stored in the storage device. These specify the specific heat capacity for each substance as a polynomial as a function of temperature. For example, an average can be calculated over a temperature range of 300 to 1000 K. Since the inert component can represent a gas mixture, the specific heat capacity cpinertGas can be obtained as a mass-weighted (relative to the inert component) sum of the specific heat capacities of the components. Components that can be determined include, for example, the mass of unburned oxygen, which is the difference between the mass of atmospheric oxygen and mo2,verbr, and the mass of nitrogen, which can be determined from the air mass according to the atmospheric fraction.For this purpose, the nitrogen oxide mass can be determined using a nitrogen oxide sensor in the exhaust system 11, or via a broadband lambda probe and suitable modeling of the nitrogen oxides dependent on the fuel-air mixture. However, it is also possible to neglect components with a proportion of less than or equal to 5%, such as nitrogen oxides, when determining cpinertGas.

[0099] The temperature in the inflow line 6 can be determined using a temperature sensor for measuring the temperature in the inflow line.

[0100] The compression ratio E is known as a geometric quantity dependent on the piston stroke of the piston 5, and can be stored in the storage device as the ratio of combustion chamber volume at bottom dead center to combustion chamber volume at top dead center.

[0101] Finally, the specific heat capacity of the mixture cpGemisch in the combustion chamber can be determined in a similar way to the specific heat capacity cpinertGas, whereby a mass-weighted sum of the individual specific heat capacities relative to the total mass can be determined.

[0102] Finally, the specific gas constant of the mixture can be calculated as the ratio of the general gas constant to the molar mass of the entire mixture, whereby the individual masses can be determined as explained above, whereby a mass fraction-weighted sum of the individual molar masses stored in the storage device can be determined.

[0103] The above computing processes can be carried out, for example, in the computing unit of the control device 15.

[0104] For the combustion temperature Vk, a combustion energy and heat capacity of the inert component is determined in formula (1) according to step a) of this disclosure.

[0105] The heat capacity does not need to be determined for the entire inert portion. Components of the inert portion can also be neglected.

[0106] The determination of the above parameters is not limited to the methods described above. For example, the expected heat capacity can also be determined experimentally through bench tests before the engine is operated. The combustion energy can also be determined by performing a power balance in the combustion chamber.

[0107] If an inert agent is added that undergoes a phase transformation, such as a liquid inert agent, the fraction in Formula 1 can be as in Formula T below: In this case, the numerator is reduced by the enthalpy required for the phase transformation rninermittei * HPU, where HPU represents the specific enthalpy for the phase transformation (evaporation).

[0108] In the denominator, m InertGas * cp InertGas a component of the phase-changed inert agent.

[0109] Fig. 2 shows a flowchart of a control system that uses the combustion temperature Vk. Specifically, the combustion temperature is controlled and regulated according to the method shown in Fig. 2. The combustion temperature is therefore both the controlled variable and the regulated variable.

[0110] First, in a step S1, a permissible combustion temperature range [T1; T2] is defined. This is limited at least on one side, preferably upwards, but can also be limited at the top and bottom by T1 and T2 on both sides. The combustion temperature range [T1; T2] can, for example, be limited upwards depending on permissible nitrogen oxide emissions and / or the maximum exhaust gas temperature, and can be limited downwards depending on a minimum exhaust gas temperature for proper operation of the catalytic converter device 12. The temperature range can also vary depending on the engine's operating time.

[0111] In step S2, a target fuel quantity / mass is determined based on a power demand. In an engine with multiple combustion chambers, the target fuel quantity can be determined, for example, from a total power demand, with which a total fuel quantity correlates, by dividing by the number of combustion chambers.

[0112] With the specified fuel quantity, the mixture in the combustion chamber is known by taking into account the current air quantity and the EGR quantity as above.

[0113] Thus, the combustion temperature Vk can be determined in step S3. In step S4, Vk is compared with the permissible combustion temperature range [T1; T2].

[0114] If Vk is greater than T2, i.e., the upper limit, a comparison is made in step S5A to determine whether the ignition timing can be shifted to a later point in time. The ignition timing is determined relative to a crank angle, i.e., relative to the position of piston 5 in combustion chamber 2. It is therefore also referred to as the ignition angle.

[0115] If it is possible to shift the ignition timing backward, the ignition timing in the current combustion cycle is shifted backward in a step S5B. If a shift is no longer possible because an ignition timing limit has been reached, for example because complete combustion is no longer possible after that, the amount of fuel to be injected for the current combustion cycle is limited in a step S5C so that Vk lies within the permissible range. This can be done by temporarily reducing the specified fuel quantity. For at least one subsequent combustion cycle, at least one of an exhaust gas recirculation quantity, an inert agent supply quantity, and an air quantity can then be adjusted in a step S5D - in this case, increased. In this way, the specified fuel quantity can be reached in a subsequent cycle and Vk can remain within the permissible range.

[0116] Ignition timing as well as exhaust gas recirculation quantity, inert agent supply quantity, and / or air quantity are then manipulated variables in this order. This order is preferred, but no order is prescribed. It is also possible to adjust just one of these manipulated variables. In particular, the ignition timing can be adjusted for the current cycle, and for the subsequent cycle at least one of the exhaust gas recirculation quantity, inert agent supply quantity, and / or air quantity can be adjusted. However, depending on the design of the internal combustion engine system, it is possible to adjust one of these manipulated variables in the current cycle as well. It is also possible, as described, to adjust the power requirement / fuel quantity for the current cycle, in particular to reduce it compared to the specified fuel quantity.

[0117] Depending on the design, an inert agent can also be added and / or exhaust gas can be recirculated during the current cycle, so that the inert agent supply quantity and / or the exhaust gas recirculation quantity can also be a control variable for the current cycle. This applies in particular if the exhaust gas recirculation device and / or inert agent supply device can supply exhaust gas and / or inert gas directly into the combustion chamber, i.e., when a mixture is already present in the combustion chamber.

[0118] The control variables can thus be prioritized, with the fuel quantity, in particular, only being adjusted when one of the other control variables can no longer be adjusted. Preferably, one of the other control variables other than the fuel quantity, for example, the air quantity and / or the exhaust gas recirculation quantity and / or the inert agent supply quantity, is adjusted in the subsequent cycle.

[0119] If Vk is smaller than T1, i.e. the lower limit, a reduction in the fuel mass is no longer desirable since this limit would otherwise continue to be exceeded. In this case too, the ignition timing is shifted back in step S6 in the current cycle. Here, too, a check according to step S5A is conceivable. The associated pressure drop can ensure the lower power requirement. If an ignition timing limit is reached here, the permissible combustion temperature range can also be ensured by adjusting, in particular reducing, at least one of an exhaust gas recirculation quantity, an inert agent feed quantity, and an air quantity in at least one subsequent cycle. Here, too, an ignition timing shift is not necessarily required first.

[0120] Here, too, the exhaust gas recirculation quantity and / or inert agent supply quantity can be the control variable for the current cycle. Prioritization also occurs accordingly.

[0121] The combustion temperature Vk can be calculated based on an ignition timing parameter such as a factor in addition to formula (1). This allows the ignition timing parameter to be reduced at a later point in time. The ignition timing parameter can be determined on the test bench before the engine is operated. Thus, the combustion temperature can be determined using the ignition timing parameter so that it falls within the permissible range. However, this is optional. When determining according to formula (1), no ignition timing parameter needs to be added. If an impermissible value is found, the ignition timing is simply shifted without checking whether the changed value is a permissible one.

[0122] It should be noted that in each of the cases the ignition timing is at least after the shift, preferably also before the shift, in the expansion stroke.

[0123] In a step S7, a preset combustion temperature is determined within the permissible combustion temperature range [T1; T2]. The preset combustion temperature is preferably determined to achieve the highest efficiency and can be different from, and preferably within, the limit values ​​of the permissible combustion temperature range. Corresponding dependencies of the preset combustion temperature on the power requirement or fuel quantity can be stored in the memory device.

[0124] In steps S4 to S6, control is thus performed with respect to the combustion temperature according to step b) of the present disclosure. This preferably occurs when the power requirement changes. The control is carried out such that the specified fuel quantity, i.e., the power requirement, is reached, possibly after several cycles, and the combustion temperature is within the permissible range.

[0125] In a step S8, control is then carried out to the specified combustion temperature (which also corresponds to step b) of the present disclosure), which is preferably done at a substantially constant power requirement and over several combustion cycles, and wherein the determined combustion temperature Vk serves as a virtual sensor that feeds back the controlled variable combustion temperature. Control variables are at least one of an exhaust gas recirculation quantity, an inert agent supply quantity, and an air quantity, provided these are adjustable. Here, the combustion temperature is fed back a priori for the respective cycle, so that precise pre-control is achieved. The fuel quantity cannot be a control variable here, so the fuel quantity is the specified fuel quantity.

[0126] According to the above procedure, the combustion energy and heat capacity are determined to calculate the combustion temperature Vk. This allows a thermodynamic analysis of the combustion process to be taken into account.

[0127] In particular, the combustion temperature can be determined, controlled, and regulated. This allows the engine to be controlled with regard to emissions and efficiency. It should be noted that only one control or regulation can be performed without implementing the nested control and regulation shown in Fig. 2.

[0128] For the determination, control and / or regulation of the combustion temperature, at least one of the following parameters is used as a control variable: ignition timing, exhaust gas recirculation quantity, inert agent supply quantity, air quantity,

[0129] Power demand / fuel quantity. However, the nested control / regulation described above is advantageous.

[0130] It should be noted that the combustion temperature does not need to be determined. For example, the combustion energy and heat capacity of the inert component can be stored in a table, and a parameter of the internal combustion engine system can be controlled and / or regulated based on the table.

[0131] Fig. 5 shows a modified flow chart of the control / regulation with regard to the combustion temperature.

[0132] In Fig. 5, steps S201 to 203 essentially correspond to steps S1 to S3 in Fig. 2.

[0133] In S204, a check is made to determine whether an inert agent supply device, particularly one with phase conversion of the inert agent, is available for the corresponding combustion chamber, such as a water supply device. This can be an implemented query or can be stored in advance in a memory device, such as the memory device of a vehicle's control unit. If no water supply is present, a check is made in S205B to determine whether Vk exceeds the maximum permissible temperature T2.

[0134] If this is the case, in a step S206BA, the fuel mass is reduced so that Vk assumes the value of T2.

[0135] If this is not the case, it can be checked in a step 206BB whether Vk is greater than a permissible value of the combustion temperature for maximum nitrogen oxides VkNOx.

[0136] If this is the case, the specified fuel quantity is supplied in step 207BBA, which is therefore not adjusted, and the ignition timing is adjusted, i.e., retarded compared to a specified ignition timing. The ignition timing is adjusted based on a difference between Vk and VkNOx.

[0137] If this is not the case, the specified fuel quantity can be supplied to the combustion chamber in a step S207BBB.

[0138] Otherwise, if it is determined in step S204 that a water supply for the combustion chamber is present, the comparison of S205B can be carried out in a step S205A.

[0139] If Vk is greater than T2, the water supply in 206AA is activated and a water supply quantity into the combustion chamber (inert agent supply quantity) is adjusted so that Vk is less than or equal to T2.

[0140] Then, in a step S207AA, it can be checked whether the required water quantity mH20, which is needed here to reach T2, is greater than or equal to the maximum possible water supply quantity mH20max.

[0141] If this is not the case, water can be added to reduce nitrogen oxides, just as in the case where Vk is less than or equal to T2. In this case, a check can be carried out in step S208AB to determine whether Vk is greater than the permissible combustion temperature value for maximum nitrogen oxides VkNOx.

[0142] If this is the case, a quantity of water is added in step S209ABA such that Vk equals VkNOx, or such that mH20 equals mH20max. The specified fuel quantity cannot be adjusted in this case.

[0143] If this is not the case, the specified fuel quantity will be supplied in a step S209ABB without any further water supply.

[0144] In this case, the inert agent supply quantity is prioritized over the fuel quantity as a control variable. This allows a specified fuel quantity to be supplied reliably. Alternatively, instead of the water supply, the air quantity and / or the exhaust gas recirculation quantity can be adjusted and prioritized over the fuel quantity.

[0145] Likewise, in Fig. 5, control is initially performed relative to the permissible combustion temperature range and then regulated relative to the nitrogen oxide-optimal combustion temperature, which corresponds to pre-control. This means that if the combustion temperature is within a permissible range in steps 205A and 205B, the control process is similar to that in Fig. 2, i.e., particularly with a constant power demand. If the combustion temperature is outside the permissible range, control initially takes place within the permissible range instead of within the permissible range. Control can occur with a changing power demand.

[0146] Fig. 6 shows a flow chart for reducing knock based on combustion temperature.

[0147] In a step S301, knocking is present on a cylinder / combustion chamber-specific basis.

[0148] In step S302, the magnitude (strength) of a knock signal value of the specific combustion chamber is evaluated.

[0149] If it is determined in step S303 based on the magnitude of the knock signal value that knocking is present,

[0150] If this is the case, a check is carried out in step S304A to determine whether a reduction in fuel quantity compared to the specified fuel quantity of the specific combustion chamber can be added to at least one other combustion chamber of the internal combustion engine system. Thus, a check is carried out to determine whether a reduction in fuel quantity relative to the specified fuel quantity can be redistributed to at least one other combustion chamber. This check can be performed, for example, by checking whether a permissible Vk value results in the at least one other combustion chamber for the reduction quantity added to the corresponding specified fuel quantity.

[0151] If redistribution is possible, the target fuel quantity at the specific cylinder is reduced in a step S305AA, and the reduction quantity is added to at least one other combustion chamber in its subsequent cycle.

[0152] The relative redistribution relationship between the combustion chambers can be stored and, if necessary, applied in step S306AA to the subsequent determination of the respective preset fuel quantities for the combustion chambers. Thus, a proportion factor of a total preset fuel quantity can be determined for each combustion chamber, and corresponding preset fuel quantities for the individual combustion chambers can be determined from a subsequent total preset fuel quantity using the proportion factor.

[0153] If redistribution is not possible, a step S305AB checks whether an exhaust gas recirculation quantity can be increased, in particular whether EGR is less than EGRmax.

[0154] If an increase in the exhaust gas recirculation quantity is possible, the exhaust gas recirculation quantity is increased in a step S306ABA.

[0155] If it is not possible to increase the exhaust gas recirculation quantity, the fuel quantity is reduced compared to the specified fuel quantity in a step S306ABB.

[0156] In other cases, the flow returns to step S301.

[0157] It should be noted that in steps S305AA, S306ABA, and S306ABB, the respective parameters—fuel quantity and exhaust gas recirculation quantity—are adjusted based on the combustion temperature. In other words, the respective parameters are determined, controlled, and / or regulated based on the combustion temperature and the knock signal value.

[0158] In particular, a corresponding difference in combustion temperature can be determined depending on the magnitude of the knock signal value. This difference can be determined based on characteristic maps in which a corresponding difference in combustion temperature is assigned to the magnitude of the knock signal value. A plurality of characteristic maps can be provided for different combustion temperatures. The at least one characteristic map can be determined experimentally or by simulation.

[0159] Based on the determined difference, a target combustion temperature can be determined. The determined target combustion temperature can be determined, for example, by subtracting the previously determined combustion temperature difference from a reference combustion temperature. The reference combustion temperature can, for example, be the last determined combustion temperature in the previous cycle or can be a limit value of the permissible combustion temperature range. If no map is assigned to the reference combustion temperature, the difference can be determined by interpolation or extrapolation, or by assigning the nearest map. It should be noted that the target combustion temperature for knock reduction is not the same as the target combustion temperature in the control system shown in Fig. 2.Using the specified combustion temperature, the corresponding parameter, exhaust gas recirculation quantity and fuel quantity, can then be determined so that the specified combustion temperature is reached.

[0160] To reduce knocking, the parameters are prioritized according to the sequence shown in Fig. 6, i.e., first, a redistribution, then an increase in the exhaust gas recirculation quantity, and then a reduction in the fuel quantity. However, other sequences are also conceivable.

[0161] Furthermore, the inert agent supply quantity and / or air quantity for knock reduction can be determined based on the combustion temperature and then controlled and / or regulated.

[0162] Fig. 3 shows a flow chart for determining an ignition timing, also using the combustion temperature.

[0163] To do this, a combustion center point is first determined in step S100. The combustion center point defines the point in time, for example, in relation to the crank angle, at which a predetermined combustion conversion rate is reached. This means the point in time at which a predetermined proportion of the fuel has been burned.

[0164] It is advantageous if the specified combustion conversion rate for determining the combustion duration is always 50%.

[0165] In a step S101, the combustion duration up to the time specified in S100 is then determined. For this purpose, the combustion temperature Vk is advantageously used. The combustion temperature allows a conclusion to be drawn about the combustion duration. For a given mixture, the combustion temperature Vk can be determined as above. Characteristic curves can be determined on the test bench or by simulation before operation of the internal combustion engine system, which indicate the dependence of the duration up to the combustion conversion rate. The respective combustion temperature is preferably also determined based on formula (1), i.e., based on the combustion chamber volume. Such a characteristic curve is shown in Fig. 4.

[0166] The X-axis represents the combustion temperature Vk normalized to a reference value and the Y-axis represents the combustion duration normalized to a reference value, which without standardization has a difference in the crank angle as its unit.

[0167] As can be seen, the curve is approximately monotonically decreasing, with the duration decreasing with increasing combustion temperature. In addition to the characteristic curve, the combustion duration can be determined based on a speed parameter, which can also be determined on the test bench. This allows the turbulence occurring in the combustion chamber, which is influenced by the speed, to be taken into account when determining the duration.

[0168] Finally, during operation, the duration to be expected at the corresponding speed can be determined by means of the duration-temperature dependency stored in the memory device, which can also be available as a table.

[0169] In step S102, the duration is then subtracted from the predetermined time at which the combustion conversion rate is reached, and the ignition time is obtained.

[0170] In the process shown in Fig. 3, a combustion conversion rate is controlled based on the combustion temperature by determining the ignition timing.

[0171] It should be noted that the combustion duration does not need to be determined in the process shown in Fig. 3. The duration can also be determined based on the combustion lambda and the EGR flow rate by determining and storing corresponding characteristic curves. However, this increases the storage requirements, as this control system has multiple input variables. Alternatively, the combustion energy and the heat capacity can also serve as input variables for determining the duration.

[0172] Knock control can also be implemented in the method shown in Fig. 3 by using a knock signal value for combustion chamber 2. Depending on the knock signal value, the predetermined time at which the 50% combustion conversion rate is to be reached can be set. The higher the value, the later this time can be set.

[0173] The above methods are not limited to internal combustion engine systems that use exclusively hydrogen as fuel. Other gaseous and / or liquid fuels, such as fossil fuels, can also be used. The internal combustion engine system is preferably spark-ignited, but can also be self-igniting.

[0174] Further components can be added to the internal combustion engine system. For example, the internal combustion engine system can include components located downstream of engine 1 in terms of power or flow, such as a transmission or an exhaust, whose parameters are controlled based on the determination made in a). The control device can also include an output unit that can visually and / or acoustically output the determined heat capacity and combustion energy or a parameter determined based thereon, such as the combustion temperature. The output can be continuous, in particular for each combustion chamber and for each combustion cycle, or discrete, i.e. only at certain times or when a permissible range is exceeded. This also allows the user to be informed of the thermodynamic state in the combustion chamber and react accordingly, for example by adjusting the power requirement.

[0175] Specific heat capacities can also be determined by methods other than NASA polynomials. For example, other reference data can be used, which can be in analytical or discrete-value form.

Claims

Claims:

1. A method for operating an internal combustion engine system operated with fuel, preferably hydrogen, which has a combustion chamber (2) in which a fuel-air mixture is burned, the method comprising: a) determining a combustion energy as an energy released with the combustion of the fuel, and an inert component heat capacity as a heat capacity of at least part of an inert component of a combustion chamber content, and b) determining and / or controlling and / or regulating and / or outputting at least one parameter of the internal combustion engine system based on the determined combustion energy and the determined heat capacity.

2. The method according to claim 1, wherein the combustion energy is determined based on a calorific value of the fuel.

3. The method according to claim 1 or 2, wherein the inert fraction heat capacity is determined based on at least a portion of a mass fraction of the inert fraction.

4. The method according to any one of the preceding claims, wherein the inert fraction heat capacity is determined based on a composition of the inert fraction.

5. The method of claim 4, wherein the inert fraction heat capacity is determined based on component-specific heat capacities of components of the composition.

6. Method according to at least one of the preceding claims, wherein a combustion temperature is determined based on a ratio of combustion energy and inert fraction heat capacity, and b) is carried out based on the determined combustion temperature.

7. The method according to claim 6, wherein, to determine the combustion temperature, a final compression temperature is further determined, which is a temperature at maximum compression of the fuel-air mixture.

8. The method of claim 6 or 7, wherein the at least one parameter comprises the combustion temperature.

9. The method according to claim 8, wherein a comparison is carried out between the determined combustion temperature and a permissible combustion temperature range, and when the permissible combustion temperature range is left, an ignition point for the combustion chamber and / or a fuel quantity and / or an air quantity and / or an exhaust gas recirculation quantity and / or an inert agent supply quantity is adjusted, wherein preferably the combustion temperature is additionally determined based on an ignition point parameter, and / or a fuel quantity is adjusted when an ignition point limit is reached.

10. The method according to claim 8 or 9, wherein, preferably within the permissible combustion temperature range, control is carried out to a preset combustion temperature, in particular by adjusting an air quantity and / or an exhaust gas recirculation quantity and / or an inert agent supply quantity into the combustion chamber.

11. The method according to any one of claims 6 to 10, wherein the at least one parameter is determined, controlled and / or regulated based on the combustion temperature and a knock signal value of the combustion chamber (2), in particular an amount thereof, wherein in particular the at least one parameter comprises the fuel quantity and / or the exhaust gas recirculation quantity and / or the inert agent supply quantity.

12. The method according to claim 11, wherein a default combustion temperature is determined based on the knock signal value, and the at least one parameter is determined, controlled and / or regulated based on the default combustion temperature, in particular the target combustion temperature is determined based on a difference to a reference combustion temperature, and / or the target combustion temperature depends on the reference combustion temperature and / or the knock signal value.

13. A method for operating an internal combustion engine system powered by fuel, preferably hydrogen, having a combustion chamber (2) in which a fuel-air mixture is burned, the method comprising: Determining a combustion duration from an ignition point to a predetermined point in time at which a predetermined combustion conversion rate is reached, at which a predetermined portion of the fuel in the combustion chamber is burned, and Determining an ignition timing based on the determined combustion duration.

14. The method according to claim 13, wherein the predetermined combustion conversion rate is in a range of 30 to 70%, preferably 40 to 60%, particularly preferably 50%.

15. The method according to claim 13 or 14, wherein the combustion duration is determined based on the combustion temperature of claim 6 or 7.

16. The method according to at least one of claims 13 to 15, wherein the predetermined time is predetermined based on a knock signal value of the combustion chamber, in particular in the case of a knock signal value indicating stronger knocking, the predetermined time is shifted to a later time.

17. Control device configured to carry out a method according to at least one of the preceding claims in an internal combustion engine system.

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