Capture lambda control

Abstract

To provide an engine control unit, an internal combustion engine, and a method for controlling an internal combustion engine. [Solution] The engine control unit 10 comprises a VCR system 20 and an EGR system 30, and receives beta data from at least one beta sensor 21 indicating combustion speed, and lambda data from at least one lambda sensor 31 indicating captured lambda value, and determines the beta value based on the beta data, and determines the captured lambda value based on the lambda data. It also generates a VCR control signal 22 to be sent to the VCR system 20 indicating the compression ratio to be set, and / or generates an EGR control signal 32 to be sent to the EGR system 30 indicating the EGR rate to be set. The VCR control signal 22 and / or EGR control signal 32 are based on the beta difference between the beta value and the target beta value, and on the lambda difference between the captured lambda value and the target captured lambda value.

Description

[Technical Field]

[0001] The present invention relates to an engine control unit in the general terms of claim 1, an internal combustion engine including such an engine control unit, and a method for controlling an internal combustion engine.

[0002] The present invention preferably relates to an internal combustion engine, such as a large ship or marine engine or stationary engine, whose cylinder has an inner diameter of at least 200 mm. The engine is preferably a two-stroke engine or a two-stroke crosshead engine. The engine may be a diesel engine or a gas engine, a compound fuel engine, or a multi-fuel engine. Combustion of liquid fuel and / or gaseous fuel in such an engine is possible as well as by autoignition or forced ignition.

[0003] An internal combustion engine can be a two-stroke engine that is longitudinally scavenged.

[0004] The term internal combustion engine also refers to a large engine that can operate not only in diesel mode, characterized by fuel autoignition, but also in Otto mode, characterized by fuel forced ignition, or a combination of both. Furthermore, the term internal combustion engine includes, in particular, compound fuel engines and large engines in which fuel autoignition is used for the forced ignition of another fuel. Forced ignition can be achieved by the use of a pre-chamber, a spark plug, and / or pilot fuel.

[0005] The engine speed is preferably less than 800 RPM, especially for four-stroke engines, and more preferably less than 200 RPM, especially for two-stroke engines, which indicates a low-speed engine designation.

[0006] The fuel may be diesel fuel, marine diesel fuel, heavy oil, emulsion, slurry, methanol, or ethanol, as well as gases such as liquefied natural gas (LNG), liquefied petroleum gas (LPG), natural gas (NG), or petroleum gas (PG).

[0007] Further possible fuels that may be added to the requirements are liquefied biogas (LBG), biological fuels (e.g., oil made from algae or seaweed), ammonia, hydrogen, and synthetic fuels derived from CO2 (e.g., produced by power-to-gas or power-to-liquid). [Background technology]

[0008] Large vessels, especially those used for transporting goods, are typically powered by internal combustion engines, specifically diesel and / or gas engines, which are primarily two-stroke crosshead engines.

[0009] In reciprocating piston combustion engines, the exhaust gas recirculation (EGR) rate and compression ratio are important parameters that affect combustion, thermal efficiency, and exhaust gas emissions.

[0010] EP3081790 discloses a compound fuel combustion engine in which the occurrence of premature ignition can be controlled by introducing an inert gas or exhaust gas.

[0011] The EGR path of the exhaust gas recirculation system connects the exhaust outlet of the cylinder to the air inlet of the cylinder. The air inlet of the cylinder may also be a scavenge air receiver.

[0012] The exhaust outlet of a cylinder may be connected to an exhaust manifold, which is a place where the exhaust gases from two or more cylinders are collected.

[0013] The engine may be equipped with a low-pressure or high-pressure exhaust gas recirculation system. In engines using high-pressure EGR, the exhaust gas is taken directly from the exhaust manifold and combined with fresh intake air just before entering the engine. In the case of low-pressure EGR, the exhaust gas mass passes through the turbine of a turbocharger in particular and optionally through an exhaust gas treatment system.

[0014] EGR provides an effective means of reducing flame temperature and NOx emissions. However, engine thermal efficiency tends to decrease with EGR as a result of reducing the work drawn and increasing the work pumped.

[0015] Generally, the air-fuel ratio, or lambda number (λ), is related to the stoichiometric air-fuel ratio and thus determines the mass ratio of air to fuel. Ideally balanced combustion conditions result in neither oxygen deficiency nor excess. Therefore, classical lambda closed-loop control can provide a stoichiometric air-fuel mixture for combustion in spark-ignition engines.

[0016] In premixed gasoline (automotive) engines operating with catalytic converters, a lambda number of approximately 1 is typical.

[0017] For large engines in gas mode with so-called premixed lean-burn combustion, the appropriate lambda value is rather around 2. For engines without EGR and VCR, a lambda number close to 1 will result in a high combustion rate. A higher lambda number allows the combustion rate to be reduced to a level where the components involved are not harmed by high temperatures and pressure peaks. Furthermore, NOx emissions are kept within acceptable limits.

[0018] The lambda number may represent a setpoint control value for both exhaust gas recirculation and catalytic exhaust gas scrubbing.

[0019] In large diesel engines, scavenging or charging is usually provided by a turbocharger that generates a scavenging or charging pressure, which depends on the load of the engine and thus on the output or torque or speed of the engine. For a given charging pressure, the mass of air in the cylinder can be calculated, and then an appropriate amount of gaseous fuel can be determined for each required driving torque or desired speed generated by the engine, this appropriate amount resulting in an optimal combustion process for this operating state.

[0020] In the case of large engines operating in gas mode according to the Otto principle, the optimal lambda value can be, for example, between 2.0 and 3.0, preferably between 2.3 and 3.0. The limitation on the lambda value can vary slightly depending on the load at which the engine is operated.

[0021] The compression ratio of an external combustion engine represents the ratio of the volume from the maximum volume to the minimum volume of the combustion chamber of the external combustion engine. In a piston engine, the compression ratio is the ratio of the volume of the combustion chamber when the piston is at the bottom (bottom dead center) of its stroke to the volume of the combustion chamber when the piston is at the top (top dead center) of its stroke. Thus, the compression ratio may be calculated by the ratio of the sum of the displacement volume and the clearance volume to the clearance volume. The displacement volume is the volume inside the cylinder displaced by the piston from the start to the end of the compression stroke. The clearance volume is the volume of the space remaining in the cylinder at the end of the compression stroke.

[0022] Instead of the compression ratio as described above, which may also be regarded as the geometric compression ratio, an "effective compression ratio" may also be specified. The "effective compression ratio" takes into account only the compression after the exhaust valve is closed and thus the "effective compression ratio" is less than or equal to the "geometric compression ratio".

[0023] The compression ratio is usually selected to yield the best engine performance. High-load engine performance is often the most relevant consideration for the selection. A variable compression ratio is desirable for optimal performance over the entire operating range.

[0024] A variable compression ratio (VCR) system is a system for increasing or decreasing the compression ratio of a piston during operation, as disclosed in, for example, EP2687707A2. A geometric VCR system may include a drive mechanism on the piston, on the crosshead, on the crosshead pin, and / or on the cylinder head, whereby the physical geometry of the combustion chamber may be changed. Specifically, the drive mechanism may include a hydraulic actuator on the crosshead. The drive mechanism advantageously adjusts the geometric compression ratio of the engine by physically changing the volume of the space above the piston disposed at top dead center.

[0025] Optimal engine performance may be achieved at an optimal combustion speed.

[0026] EP3748144A1 discloses a method for operating a large engine in which an optimized compression ratio for an air-fuel mixture is determined based on operating parameters and the compression ratio is converted to the optimized compression ratio.

Prior Art Documents

Patent Documents

[0027]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0028] Therefore, an object of the present invention is to provide an engine control unit, an internal combustion engine, and a method for operating an internal combustion engine that at least partially avoid the drawbacks of prior art solutions and in particular enable a more stable engine control method.

Means for Solving the Problems

[0029] The objective is achieved by the engine control unit described in claim 1.

[0030] The engine control unit is for a large reciprocating piston combustion engine having at least one cylinder with an inner diameter of at least 200 mm.

[0031] The engine control unit is for a large reciprocating piston combustion engine, which includes a VCR system at the crosshead, particularly a geometric VCR system, preferably a hydraulically operated geometric VCR system, and an EGR system.

[0032] Typically, the compression ratio may be in the range of 14 and 25. The compression ratio may preferably be continuously controlled by a hydraulic valve during operation.

[0033] Typically, the piston is movably positioned within the cylinder liner, and the crankshaft is rotatably positioned within the crankshaft housing. The piston is connected to the crosshead via a piston rod, and the crosshead is connected to the crankshaft via a connecting rod to drive the crankshaft. The drive mechanism of the VCR system may achieve displacement of the piston rod relative to the crosshead, or may be located within the crosshead.

[0034] The drive mechanism of the VCR system may include a hydraulic cylinder located at the lower end of a piston rod, and a hydraulic piston that moves up and down within the hydraulic cylinder.

[0035] The EGR system enables the increase or decrease of the EGR rate. The EGR system may include an adjustable exhaust gas valve, an adjustable blower, and / or an adjustable back pressure valve for setting the EGR rate.

[0036] Specifically, the EGR rate may be continuously controlled via a large butterfly valve that adjusts the pressure drop in the EGR path relative to the exhaust path.

[0037] The engine control unit is configured to receive beta data from at least one beta sensor indicating the combustion rate.

[0038] The beta sensor provides data for calculating the beta value. The beta value represents the combustion rate, for example, given by pressure per crank angle (bar / °[CA]). The beta sensor may be a pressure sensor or may include a pressure sensor that provides combustion chamber pressure data with respect to time or crank angle, respectively.

[0039] The engine control unit is configured to receive lambda data from at least one lambda sensor indicating a trapped lambda value.

[0040] At least one lambda sensor provides data for calculating the captured lambda value. The at least one lambda sensor may be an oxygen sensor or an oxygen sensor.

[0041] The term "lambda" generally refers to the overall stoichiometric air-fuel ratio. Typically, in internal combustion engines, lambda is calculated by dividing total air consumption by total fuel consumption. In large two-stroke engines, "over-scavenging" should be considered, meaning that the mass of air flowing through the cylinder per cycle significantly exceeds the mass of air captured after the exhaust valve closes. Therefore, it is more useful to refer to the "captured lambda value," i.e., the stoichiometric air-to-fuel ratio, which represents the mass of captured air.

[0042] While the beta value may be calculated based on a signal measured by a pressure sensor, such as a cylinder pressure sensor, the captured lambda value is typically calculated based on several signals, primarily an oxygen sensor.

[0043] A commonly applied type of lambda sensor measures the total air-to-fuel ratio by measuring excess oxygen in the exhaust. However, as mentioned above, this does not correspond to captured lambda.

[0044] To measure the captured lambda value, an oxygen sensor may be placed inside the scavenging receiver, where the oxygen concentration may be reduced by EGR.

[0045] The amount of fuel and the mass of captured air may be determined by applying an engine model and considering temperature and pressure signals. The captured stoichiometric air-to-fuel ratio for each cycle may be calculated, taking into account the measured oxygen concentration.

[0046] Alternatively, or furthermore, the oxygen / lambda sensor may be located in the exhaust pipe instead of in the scavenging receiver.

[0047] The engine control unit is configured to determine the beta value based on beta data and to determine the captured lambda value based on lambda data.

[0048] The engine control unit is configured to generate a VCR control signal to be sent to a VCR system indicating the compression ratio to be set, and / or to generate an EGR control signal to be sent to an EGR system indicating the EGR rate to be set. The VCR control signal and / or EGR control signal are based on the beta difference between the beta value and the target beta value, and / or the lambda difference between the captured lambda value and the target captured lambda value.

[0049] The engine control unit may be configured to determine that VCR control signals and / or EGR control signals have been generated in accordance with the beta difference and / or lambda difference.

[0050] Increasing the compression ratio typically increases the combustion rate, which can lead to high pressure. This high pressure must be limited to avoid overloading the mechanical components.

[0051] Changes in EGR can result in changes in the captured lambda value and altered combustion rates. The latter can be compensated for by changing the compression ratio.

[0052] By optimizing the compression ratio and EGR rate, it may be possible to achieve minimum fuel consumption and ultimately minimum methane emissions.

[0053] Since a new beta value is obtained faster than a new captured lambda value, the VCR control loop may be considered faster than the EGR control loop. In other words, the VCR control signal may be generated at a higher (refresh) rate than the EGR control signal. Therefore, the control loops may be coupled, but not of equivalent rank. The VCR control may be of a higher rank than the EGR control (i.e., preferential to the EGR control).

[0054] Specifically, changes in the VCR control signal may result in a corresponding reaction with a combustion rate 5 to 100 times, preferably 10 times, faster than changes in the EGR control signal and / or the captured lambda value response to the changes in the VCR control signal.

[0055] The engine control unit may be configured to generate VCR control signals faster than EGR control signals (at a higher refresh rate). Specifically, VCR control signals are generated 5 to 100 times, and preferably 10 times, more frequently than EGR control signals.

[0056] The target acquisition lambda value may be in the range of 1 to 1.5, and especially in the range of 1.1 to 1.2.

[0057] The target acquisition lambda value may be set and remain independent of the fuel used or any ambient conditions.

[0058] Generally, the beta value can take values ​​within the range of 0 bar / °[CA] to 10 bar / °[CA], in which case 0 bar / °[CA] corresponds to a misfiring event.

[0059] The target beta value may be in the range of 5 bar / °[CA] to 10 bar / °[CA], specifically 4 bar / °[CA] to 8 bar / °[CA], preferably 6 bar / °[CA].

[0060] The target beta value may depend on the fuel used.

[0061] The engine is preferably always operated at a captured lambda value as close to 1.0 as possible without ever falling below 1.0. Below 1.0, there is a risk that the engine speed control will no longer be able to function properly, potentially leading to increased emissions of unburned fuel.

[0062] The VCR control signal and / or EGR control signal may include a step direction and a step size for changing the EGR rate and / or compression ratio.

[0063] The engine control unit may be configured to determine the direction and / or amount of change for changing the EGR rate and / or compression ratio in accordance with the beta difference and / or lambda difference.

[0064] The engine control unit may include at least one PID control device for controlling the compression ratio and / or EGR rate, specifically, separate PID control devices for the compression ratio / VCR control signal and the EGR rate / EGR control signal, respectively.

[0065] The amount used to change the EGR rate and / or compression ratio may be a predetermined step size.

[0066] Specifically, the engine control unit is configured to generate a VCR control signal sent to the VCR system such that an increase in the compression ratio is triggered when the beta value is below a predetermined target beta value.

[0067] An increased compression ratio typically results in a higher combustion rate.

[0068] Similarly, the engine control unit may be configured to generate VCR control signals sent to the VCR system such that a reduction in the compression ratio is triggered when the beta value exceeds a target beta value.

[0069] A reduced compression ratio typically results in a lower combustion rate.

[0070] The greater the difference between the beta value and the predetermined target beta value, the larger the step size required to change the compression ratio may be. PID control may be used.

[0071] The engine control unit may be configured to generate an EGR control signal to trigger an increase in the EGR rate when the captured lambda value exceeds a target captured lambda value.

[0072] An increased EGR rate typically results in a lower captured lambda value.

[0073] The engine control unit may be configured to generate an EGR control signal to cause a reduction in the EGR rate when the captured lambda value is less than the target captured lambda value.

[0074] A reduced EGR rate typically results in a higher captured lambda value.

[0075] The greater the difference between the captured lambda value and the target captured lambda value, the larger the step size may be required to change the EGR rate. PID control may be used.

[0076] Alternatively, the engine control unit may be configured to generate an EGR control signal depending on the beta value and a VCR control signal depending on the captured lambda value.

[0077] Specifically, the engine control unit may be configured to generate a VCR control signal to cause a change in the compression ratio when the captured lambda value differs from the target captured lambda value.

[0078] The greater the difference between the captured lambda value and the predetermined target captured lambda value, the larger the step size may be for changing the compression ratio. PID control may be used.

[0079] The engine control unit may be configured to generate an EGR control signal to cause a change in the EGR rate when the beta value differs from the target beta value.

[0080] The greater the difference between the beta value and the target beta value, the larger the step size may be required to change the EGR rate. PID control may be used.

[0081] In this case, the EGR control signal may be generated at a higher (refresh) rate than the VCR control signal.

[0082] The engine control unit may be configured to generate a VCR control signal to be sent to the VCR system as long as the lambda difference is less than a predetermined threshold, preferably less than 0.5, particularly less than 0.1, or as long as the captured lambda value is within the range of 1 to 1.5, particularly within the range of 1.1 to 1.2, and not to generate an EGR control signal and / or not to send an EGR control signal to the EGR system.

[0083] Therefore, as long as the captured lambda value is close to 1 and not less than 1.0, the EGR rate does not need to be changed, and any further optimization may be achieved only by changing the compression ratio.

[0084] However, as a result of changes in the compression ratio, or any other event such as changes in the operating mode or weather conditions, the captured lambda value may exceed the lambda threshold and deviate from the target captured lambda value. In this case, the EGR rate needs to be changed, which may also necessitate a change in the compression ratio to keep the beta value within an appropriate range.

[0085] The engine control unit may apply two control loops to stabilize the lambda difference and the beta difference.

[0086] The engine control unit may be configured to generate an EGR control signal so as to minimize the lambda difference, and a VCR control signal so as to minimize the beta difference. The creation of the VCR control signal may be performed as a lower-level control loop or as a higher-level control loop to the creation of the EGR control signal.

[0087] Alternatively, the engine control unit may be configured to generate an EGR control signal so as to minimize the beta difference, and a VCR control signal so as to minimize the lambda difference. The generation of the EGR control signal may be carried out as a lower-level or higher-level control loop than the generation of the VCR control signal.

[0088] The engine control unit may be configured to receive and / or store a target beta value and / or a target acquisition lambda value and / or an arbitrary threshold.

[0089] A user may wish to change one or more of the target beta value and / or target acquisition lambda value and / or threshold values, for example, due to modified operating parameters, and may input the new values ​​for each of these into the engine control unit.

[0090] The target beta value and / or the target capture lambda value and / or the threshold may be stored in a table along with the respective engine operating parameters. If the operating parameters, such as engine load, are changed, a new target beta value and / or the target capture lambda value and / or the updated threshold may be set.

[0091] The table and / or any other values ​​may be determined during a shop trial and stored thereafter, or they may be remotely updated / uploaded during use, for example, via a satellite data connection.

[0092] The engine control unit may be configured to set a target beta value depending on the fuel used.

[0093] The beta data may include pressure data as a function of the crank angle provided by a pressure sensor. The pressure sensor is preferably arranged in the cylinder. The pressure sensor may also be arranged in the exhaust manifold.

[0094] It may also be an option to derive a value indicating the combustion rate from other sources such as a sensor for NOx emissions.

[0095] The beta value may be obtained by an increase in the pressure data with respect to the crank angle in the region of the crank angle before the pressure reaches its maximum value.

[0096] The increase may be determined by calculating the derivative or slope of the pressure data with respect to the crank angle in the region of the crank angle before the pressure reaches its maximum value. The maximum derivative may be selected to determine the beta value.

[0097] The increase may be determined by dividing the difference between the maximum pressure p max and the reference pressure p c by the difference between the crank angle θpmax at which the maximum pressure occurs and the crank angle θ PIT Beta = (p max - p c ) / (θ pmax - θ PIT )

[0098] The crank angle θ PIT may correspond to the crank angle at which a pilot firing event such as pilot fuel injection starts.

[0099] Alternatively, the crank angle θ PIT may correspond to the crank angle at which combustion starts. The reference pressure p c ​This may correspond to the particularly estimated maximum compression pressure in the cylinder.

[0100] An increase in pressure data indicates a higher rate of combustion. The faster the combustion, the faster the pressure rises.

[0101] The lambda data may include oxygen data provided by an oxygen sensor located in the air inlet of the cylinder. Alternatively, the oxygen sensor or lambda sensor may be located in the exhaust gas, for example, in the exhaust gas manifold.

[0102] Lambda data is - Pressure data showing the scavenging pressure inside the cylinder, - Temperature data showing the scavenging temperature inside the cylinder, and - Temperature data showing the temperature of the exhaust gas upstream of the turbine It may further include at least one of the groups.

[0103] The captured lambda value is, - In particular, the power source, which is the shaft power of the engine, - In particular, the rotational speed of the engine, - Geometric compression ratio, and - Exhaust valve closing time It may be further calculated based on at least one of the groups.

[0104] The engine control unit may be configured to receive beta data from at least one beta sensor every 1 to 10 strokes.

[0105] The engine control unit may be configured to receive lambda data from at least one lambda sensor every 1 to 100 strokes, preferably every 5 to 15 strokes.

[0106] The engine control unit may be configured to generate VCR control signals every 1 to 10 strokes.

[0107] The engine control unit may be configured to generate an EGR control signal every 1 to 100 strokes, preferably every 5 to 15 strokes.

[0108] The compression ratio can typically respond quickly to changes in beta. The actual EGR rate typically responds more slowly to changes in lambda.

[0109] However, the beta value and the captured lambda value may also be sampled in real time.

[0110] The object of the present invention is also achieved by an internal combustion engine comprising at least one cylinder having an inner diameter of at least 200 mm.

[0111] The internal combustion engine further comprises a VCR system for geometrically adjusting the compression ratio, an EGR system, at least one beta sensor for measuring beta data indicating combustion speed, at least one lambda sensor for measuring lambda data indicating captured lambda value, and the engine control unit described above.

[0112] The objective is also achieved by the method for operating the internal combustion engine described above.

[0113] The method includes the following steps:

[0114] The engine control unit receives beta data from at least one beta sensor.

[0115] Lambda data is received from at least one lambda sensor.

[0116] The beta value is determined based on the beta data, and the captured lambda value is determined based on the lambda data.

[0117] A VCR control signal is generated to be sent to the VCR system indicating the compression ratio to be set. Furthermore, an EGR control signal is generated to be sent to the EGR system indicating the EGR rate to be set.

[0118] The VCR control signal and / or EGR control signal are generated based on the beta difference between the beta value and the target beta value, and / or the lambda difference between the captured lambda value and the target captured lambda value.

[0119] It is preferable that the VCR control signal and / or EGR control signal are generated such that the captured lambda value is as close to 1.0 as possible, rather than less than 1.0, without compromising the control of the value being greater than or equal to 1.0.

[0120] The VCR control signal and / or EGR control signal are preferably generated such that the captured lambda value is 1 or greater and 1.2 or less, preferably 1.1.

[0121] A VCR control signal may be sent to the VCR system, which may cause an increase in the compression ratio when the beta value is less than a predetermined target beta value, and / or cause a decrease in the compression ratio when the beta value exceeds a predetermined target beta value.

[0122] An EGR control signal may be sent to the EGR system, which may cause an increase in the EGR rate when the captured lambda value exceeds a predetermined target captured lambda value, and / or cause a decrease in the EGR rate when the captured lambda value is less than a predetermined target captured lambda value.

[0123] As long as the lambda difference is less than a predetermined threshold, preferably less than 0.5, and particularly less than 0.1, or as long as the captured lambda value is within the range of 1 to 1.2, the VCR control signal may be sent to the VCR system, and the EGR control signal may not be sent to the EGR system.

[0124] As long as the captured lambda value is close to 1.0 and not less than 1.0, the EGR rate does not need to be changed.

[0125] The EGR control signal may be generated in such a way that the lambda difference is minimized, and the VCR control signal may be generated in such a way that the beta difference is minimized.

[0126] Alternatively, the VCR control signal may be generated in such a way that the lambda difference is minimized, and the EGR control signal may be generated in such a way that the beta difference is minimized.

[0127] The objective is also achieved by a computer program comprising program code for performing the steps of the above method when executed on the engine control unit of the internal combustion engine described above.

[0128] The problem is also solved by a computer program product that can be directly loaded into the internal memory of the digital computer, which contains a software code portion that performs the above method steps when the program is running on the digital computer of the internal combustion engine described above.

[0129] Further advantageous aspects of the present invention are described below with reference to exemplary embodiments and figures. Functionally equivalent elements are given the same reference numerals. [Brief explanation of the drawing]

[0130] [Figure 1] This is a schematic diagram of an internal combustion engine. [Figure 2] This is a schematic diagram of the beta control loop. [Figure 3] This diagram schematically shows the captured lambda control loop. [Figure 4] This figure shows the pressure curve as a function of the crank angle. [Modes for carrying out the invention]

[0131] Figure 1 shows a schematic representation of the internal combustion engine 100.

[0132] The internal combustion engine 100 comprises a cylinder 1 having an inner diameter of at least 200 mm and a reciprocating piston 6.

[0133] The internal combustion engine 100 further comprises a VCR system 20 for changing the compression ratio in cylinder 1 and an EGR system 30 for adjusting the rate of recirculated exhaust gas.

[0134] The exhaust gas exiting cylinder 1 is guided to the turbine 3 of the turbocharger 4, and can then be divided into a portion that exits the engine and a portion that is recirculated to the compressor 5 of the turbocharger 4.

[0135] An EGR valve 33 is installed to control the EGR rate.

[0136] The internal combustion engine 100 includes a beta sensor 21 for measuring beta data indicating combustion speed and a lambda sensor 31 for measuring lambda data indicating captured lambda value.

[0137] The internal combustion engine 100 includes an engine control unit 10, which is configured to receive beta data from at least one beta sensor 21 indicating combustion speed and lambda data from at least one lambda sensor 31 indicating captured lambda value.

[0138] The engine control unit 10 is configured to determine the beta value based on beta data and to determine the captured lambda value based on lambda data.

[0139] The engine control unit 10 is configured to generate a VCR control signal 22 to be sent to a VCR system 20 indicating the compression ratio to be set, and / or to generate an EGR control signal 32 to be sent to an EGR system (30) indicating the EGR rate to be set.

[0140] The VCR control signal 22 and / or EGR control signal 32 are based on the beta difference between the beta value and the target beta value and the lambda difference between the captured lambda value and the target captured lambda value.

[0141] Figure 2 schematically shows the beta control loop βL.

[0142] In the first step I, the compression ratio is either kept constant, increased by a compression ratio step ΔCR, or decreased by a compression ratio step ΔCR. The decision depends on the result of step VI (see below).

[0143] In the second step II, if the compression ratio is kept constant, the combustion rate also generally remains constant. If the compression ratio is increased or decreased, the combustion rate generally changes in the second step II.

[0144] In the third step, the pressure inside the cylinder is measured against time, i.e., against the crank angle.

[0145] In the fourth step (IV), the beta value is determined (see, for example, Figure 4).

[0146] In the optional fifth step V, the captured lambda value may be checked (see step (v) in Figure 3).

[0147] If the captured lambda value is still close to 1.0 and not less than 1.0, in step VI, the beta value is compared to the target beta value, and if necessary, the compression ratio step ΔCR is set.

[0148] The beta value may be altered due to a changed compression ratio and / or other factors such as a changed EGR rate.

[0149] Figure 3 schematically shows the capture lambda control loop λL.

[0150] In the first step (i), the EGR rate is kept constant, increased by an EGR rate step ΔEGR, or decreased by an EGR rate step ΔEGR. The determination and step size depend on the result of step (v) (see below).

[0151] The EGR rate is preferably changed by opening or closing the EGR valve 33 (see Figure 1), or by adjusting its processing volume.

[0152] If the EGR rate has been increased or decreased, generally, in step (ii), the amount of oxygen at the air inlet and / or the amount of air in the exhaust gas will change due to the modified capture lambda value.

[0153] Furthermore, the combustion rate may change, which can be compensated for in the beta control loop βL as shown in Figure 2.

[0154] In the third step (iii), at least the oxygen content in the air inlet and / or exhaust gas is measured. Further data, such as pressure data indicating scavenging pressure and / or temperature data, may be determined.

[0155] In the fourth step (iv), the captured lambda value is determined based on the value measured in step (iii).

[0156] In the fifth step (v), the captured lambda value is compared to the target captured lambda value. If necessary, the EGR step ΔEGR is set.

[0157] Figure 4 shows the combustion rate curve as a function of the crank angle, indicated by a solid line on the horizontal axis. Combustion pressure is related to the left vertical coordinate, indicated by a bar.

[0158] The dashed line represents the motoring pressure for a given crank angle without combustion.

[0159] The dotted line represents pilot injection over time and shows the behavior of the pilot injection valve with respect to the crank angle. The pilot injection curve is related to the right vertical coordinate, where the current value is in amperes [A].

[0160] An increase in combustion pressure corresponds to an increase in combustion speed.

[0161] An increase in the beta value corresponds to the maximum pressure p on the combustion pressure curve. max and the maximum compression pressure p corresponding to the maximum value of the motoring pressure curve c The difference between the two is the crank angle θ at maximum combustion pressure. pmax and the crank angle θ at the start of pilot injection PIT It may also be determined by dividing by the difference between the two. (p max -p c ) / (θ pmax -θ PIT )=β

Claims

1. An engine control unit (10) for a large reciprocating piston combustion engine (100) comprising at least one cylinder having an inner diameter of at least 200 mm and further comprising a VCR system (20) and an EGR system (30), - The engine control unit (10) To receive beta data from at least one beta sensor (21) indicating the combustion rate, And, To receive lambda data from at least one lambda sensor (31) indicating the captured lambda value, Consists of, - The engine control unit (10) To determine the beta value based on the aforementioned beta data, And, Determine the captured lambda value based on the aforementioned lambda data. Consists of, - The engine control unit (10) is configured to generate a VCR control signal (22) to be sent to the VCR system (20) indicating the compression ratio to be set, and / or to generate an EGR control signal (32) to be sent to the EGR system (30) indicating the EGR rate to be set. The VCR control signal (22) and / or the EGR control signal (32) Based on the beta difference between the aforementioned beta value and the target beta value, And / or, Engine control unit (10) based on the lambda difference between the captured lambda value and the target captured lambda value.

2. The target acquisition lambda value is in the range of 1 to 1.5, particularly in the range of 1 to 1.

1. The engine control unit according to claim 1.

3. The target beta value is in the range of 5 bar / °[CA] to 10 bar / °[CA], particularly 6 bar / °[CA]. The engine control unit according to claim 1 or 2.

4. The system is configured to generate the VCR control signal (22) and the EGR control signal (32) such that the VCR control signal (22) takes precedence over the EGR control signal (32). In particular, the engine control unit according to any one of claims 1 to 3, wherein the VCR control signal (22) is generated at a higher ratio than the EGR control signal (32) such that the reaction of the combustion speed is 5 to 100 times, preferably 10 times, faster than the reaction of the captured lambda value.

5. The aforementioned engine control unit is The VCR control signal is generated such that an increase in the compression ratio is triggered when the beta value is less than a predetermined target beta value. and / or, The VCR control signal is generated such that a decrease in the compression ratio is triggered when the beta value exceeds a predetermined target beta value. An engine control unit according to any one of claims 1 to 4.

6. The aforementioned engine control unit is The EGR control signal is generated such that an increase in the EGR rate is triggered when the captured lambda value exceeds a predetermined target captured lambda value, and / or The EGR control signal is generated such that a decrease in the EGR rate occurs when the captured lambda value is less than a predetermined target captured lambda value. An engine control unit according to any one of claims 1 to 5.

7. As long as the lambda difference is less than a predetermined threshold, preferably less than 0.5, and particularly less than 0.1, Or, As long as the captured lambda value is within the range of 1 to 1.5, and especially within the range of 1.1 to 1.2, The aforementioned engine control unit is To generate the VCR control signal, and, To prevent the generation of the aforementioned EGR control signal and / or to prevent the transmission of the aforementioned EGR control signal to the EGR system. An engine control unit according to any one of claims 1 to 6.

8. The aforementioned engine control unit is The EGR control signal is generated such that the lambda difference is minimized, and To generate the VCR control signal such that the beta difference is minimized, An engine control unit according to any one of claims 1 to 7.

9. The aforementioned engine control unit is The EGR control signal is generated such that the beta difference is minimized, and To generate the VCR control signal such that the lambda difference is minimized, An engine control unit according to any one of claims 1 to 4.

10. The engine control unit is configured to receive and / or store the target beta value and / or target acquisition lambda value. An engine control unit according to any one of claims 1 to 9.

11. The engine control unit according to any one of claims 1 to 10, wherein the beta data preferably includes pressure data as a function of crank angle provided by a pressure sensor located in the cylinder.

12. The engine control unit according to claim 11, wherein the beta value is obtained by the increase in pressure with respect to the crank angle in the region of the crank angle before the pressure reaches its maximum value.

13. The engine control unit according to any one of claims 1 to 12, wherein the lambda value includes oxygen data provided by an oxygen sensor located in the air inlet of the cylinder.

14. The aforementioned lambda data, - Pressure data showing the scavenging pressure inside the cylinder, - Temperature data showing the scavenging temperature inside the cylinder, and - Temperature data showing the temperature of the exhaust gas upstream of the turbine It further includes at least one of the groups, And / or, The aforementioned captured lambda value is, - In particular, the power which is the shaft power of the aforementioned engine, - In particular, the rotational speed of the engine, - Geometric compression ratio, and, - Exhaust valve closing time The engine control unit according to claim 13, which is calculated based on at least one of the group.

15. An internal combustion engine (100) comprising at least one cylinder (1) having an inner diameter (2) of at least 200 mm, - In particular, a VCR system (20) for geometrically adjusting the compression ratio, - EGR system (30), - At least one beta sensor (21) for measuring beta data indicating combustion rate, - At least one lambda sensor (31) for measuring lambda data indicating the captured lambda value, - An engine control unit (10) according to any one of claims 1 to 14, An internal combustion engine (100) equipped with the following.

16. A method for operating an internal combustion engine according to claim 15, wherein the method is: - The step of receiving beta data from at least one beta sensor, - The step of receiving lambda data from at least one lambda sensor, - A step of determining the beta value based on the aforementioned beta data, - A step of determining the captured lambda value based on the lambda data, - A step of generating a VCR control signal to be sent to the VCR system indicating the compression ratio to be set and / or generating an EGR control signal to be sent to the EGR system indicating the EGR rate to be set, Equipped with, A method wherein the VCR control signal and / or the EGR control signal are generated based on the beta difference between the beta value and the target beta value and / or the lambda difference between the captured lambda value and the target captured lambda value.

17. The method according to claim 16, wherein the VCR control signal is sent to the VCR system to cause an increase in the compression ratio when the beta value is less than a predetermined target beta value, and / or cause a decrease in the compression ratio when the beta value exceeds a predetermined target beta value.

18. The method according to claim 16 or 17, wherein the EGR control signal is sent to the EGR system to cause an increase in the EGR rate when the captured lambda value exceeds a predetermined target captured lambda value, and / or cause a decrease in the EGR rate when the captured lambda value is less than a predetermined target captured lambda value.

19. As long as the lambda difference is less than a predetermined threshold, preferably less than 0.5, and particularly less than 0.1, and / or, As long as the captured lambda value is within the range of 1 to 1.5, and especially within the range of 1 to 1.1, The method according to any one of claims 16 to 18, wherein the VCR control signal is sent to the VCR system and the EGR control signal is not sent to the EGR system.

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