Method and control unit for detecting abnormal combustion, in particular combustion knock, in at least one cylinder of internal combustion engine

Abstract

Method for detecting abnormal combustion, in particular combustion knock or pre-ignition, in at least one cylinder of an internal combustion engine, comprising: a step of determining cylinder-specific measurement data for each of the at least one cylinder on the basis of a measurement signal acquired by at least one vibration sensor; a step of obtaining a cylinder-specific detection configuration for each of the at least one cylinder; and a step of analyzing, for each of the at least one cylinder, the cylinder-specific measurement data based on the associated detection configuration to detect an abnormal combustion condition.

Description

Technical Field

[0001] The invention relates to a method for detecting abnormal combustion, in particular combustion knock and / or pre-ignition, in at least one cylinder of an internal combustion engine. The invention also relates to a control unit of a combustion chamber of an internal combustion engine for carrying out such a method. Background Art

[0002] In order to ensure high efficiency, the internal combustion engine is designed to burn the air-fuel mixture in its cylinder in a timely and controlled manner so as to generate peak pressure in its cylinder at an ideal time under ideal operating conditions, thereby maximizing the recovery of the work of the expanding gases produced during combustion. To this end, the ignition of the air-fuel mixture and the propagation of the flame front in the combustion chamber need to be carried out according to a strictly defined pattern. However, any deviation from the ideal operating conditions may result in a less favorable combustion of the air-fuel mixture, resulting in a deterioration in engine performance and efficiency. In the context of the present invention, any such unexpected deviation from the desired combustion process in the combustion chamber may be referred to as abnormal combustion or abnormal combustion conditions.

[0003] One particularly unfavorable combustion condition is known as "combustion knock," also known as "engine knock" or "detonation." In general, combustion knock refers to an unintended combustion phenomenon that may result when combustion of at least some of the air-fuel mixture in the combustion chamber is not initiated by the propagation of the intended flame front, but occurs outside the flame front, particularly due to an unexpected explosion.

[0004] Another adverse combustion condition is known as "pre-ignition," which, in the context of the present invention, refers to a combustion process during which combustion, and in particular the propagation of the flame front within the cylinder, occurs too early in the combustion cycle compared to predefined ideal operating conditions.

[0005] Combustion knock can be the main inherent limitation to higher power density in internal combustion engines. Operating the engine close to this combustion knock-induced limit can achieve high thermal efficiency and therefore can be a desirable operating point. However, when this limit is exceeded, combustion knock can occur, which can be detrimental to the operation of the engine.

[0006] In order to monitor and detect combustion knock during engine operation, different methods and systems are known that use vibration sensors to measure and analyze vibrations at the engine block to indirectly determine knock events. However, the measured vibrations may be caused by a variety of different phenomena and events during engine operation, which may affect the detection accuracy of such indirect methods. Summary of the invention

[0007] Starting from the prior art, an object is to provide an improved method for detecting abnormal combustion, in particular enabling a robust and reliable combustion knock detection and / or pre-ignition detection. Another object is to provide a control unit of an internal combustion engine for carrying out such a method.

[0008] These objects are solved by the subject-matter of the independent claims.Preferred embodiments are set forth in the description, the drawings and the dependent claims.

[0009] Therefore, a method for detecting abnormal combustion, in particular combustion knock and / or pre-ignition, in at least one, in particular more than one cylinder of an internal combustion engine is provided. The proposed method comprises: a step of determining cylinder-specific measurement data for each of at least one cylinder based on measurement signals acquired by at least one vibration sensor; a step of obtaining a cylinder-specific detection configuration for each of at least one cylinder; and, for each of at least one cylinder, a step of analyzing the cylinder-specific measurement data based on the associated detection configuration to detect an abnormal combustion condition in the associated cylinder.

[0010] Furthermore, a control unit of an internal combustion engine is provided for detecting abnormal combustion, in particular combustion knock and / or pre-ignition conditions, in at least one cylinder. The control unit is configured, based on measurement signals acquired by at least one vibration sensor, for determining cylinder-specific measurement data for each of the at least one cylinder, for obtaining a cylinder-specific detection configuration for each of the at least one cylinder, and for analyzing the cylinder-specific measurement data for each of the at least one cylinder based on the associated detection configuration to detect abnormal combustion conditions in the associated cylinder.

[0011] The proposed control unit is configured to perform the above-mentioned proposed method. Therefore, the technical features described herein in the context of the proposed method may also be referred to and applied to the proposed control unit, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which:

[0013] Figure 1 A schematic flowchart of a method for detecting abnormal combustion of at least one cylinder of an internal combustion engine according to an embodiment of the present invention is shown.

[0014] Figure 2 In more detail, the Figure 1 Step S3 of the method; and

[0015] Figure 3 In more detail, the Figure 1 Step S4 of the method. DETAILED DESCRIPTION

[0016] Hereinafter, the present invention will be explained in more detail with reference to the accompanying drawings. In the accompanying drawings, similar elements are denoted by the same reference numerals, and repeated descriptions thereof may be omitted to avoid redundancy.

[0017] Figure 1 A flow chart is described, showing a method for detecting abnormal combustion, i.e. abnormal combustion conditions or events, in particular combustion knock, in at least one cylinder of an internal combustion engine (hereinafter referred to as "engine"). The proposed method can be used to detect abnormal combustion conditions in any suitable engine, in particular reciprocating engines such as stationary gas engines. Therefore, the method is not limited to application to engines of a specific type or application, but can be applied between different types of engines, such as diesel engines or gas engines, and between different applications, such as engines as main engines or auxiliary engines in power plants or vehicles, etc.

[0018] Preferably, the engine monitored by the proposed method comprises a plurality of cylinders, for example four, eight, twelve or eighteen cylinders. The cylinders may be arranged in an engine block and may be defined from above by at least one cylinder head. Each cylinder may be provided with a combustion chamber defined by a piston accommodated in the cylinder. The piston may be configured for reciprocating and axial movement within the cylinder and may be coupled to a crankshaft of the engine so that the reciprocating movement of the piston is converted into a rotational movement of the crankshaft. With such a configuration, during operation of the engine, an air-fuel mixture is supplied to each cylinder and ignited in each cylinder to produce a high-pressure gas which applies a force to the associated piston and thereby axially moves the associated piston, thereby rotating the crankshaft.

[0019] The engine monitored by the proposed method also includes a control unit, also called "engine control unit" or "engine control module", which is configured to control and monitor the operation of the engine. In particular, the control unit is of the electronic control unit type and is configured to read measurement data from a plurality of sensors that monitor various engine operating parameters. In addition, the control unit is configured to process and interpret the measurement signals thus obtained, and in response, can control the actuation of a plurality of engine actuators in order to set and adjust the operating point of the engine, for example, by controlling ignition characteristics, such as the amount and composition of the air-fuel mixture supplied to the combustion chamber and ignited in the combustion chamber, ignition timing, valve drive and timing, etc. According to one configuration, the control unit may include a microcontroller for monitoring and controlling the operation of the engine. In addition, the control unit may be configured to receive and transmit information and signals via a controller area network (CAN) bus, Modbus or Ethernet.

[0020] Such an internal combustion engine and the basic structure and function of its components, in particular the basic structure and function of the control unit, are well known to those skilled in the art and are therefore not described in further detail. Instead, a method for monitoring engine operation, i.e. a method for detecting abnormal combustion conditions, is mentioned below, hereinafter referred to as the "method".

[0021] The proposed method is intended and configured for detecting abnormal combustion occurring in at least one cylinder during engine operation. In the context of the present invention, the term "abnormal combustion" refers to any unexpected deviation from the expected combustion process in the engine cylinder, in particular to a combustion knock condition or a pre-ignition condition during the cylinder operation cycle.

[0022] In the following, reference Figure 1 , details a method configured for detecting abnormal combustion in the form of combustion knock in at least one cylinder of an engine, particularly in more than one cylinder or in each cylinder. As described above, combustion knock may result when the combustion of at least some of the air-fuel mixture within the combustion chamber of the cylinder explodes outside the expected combustion front propagation during an operating cycle. In general, the term "operating cycle" refers to a combustion cycle of one cylinder, which includes the steps of: supplying an air-fuel mixture to the cylinder; combusting the air-fuel mixture; and then expelling exhaust gas from the engine. Typically, the operating cycle is associated with one or more piston strokes within the cylinder.

[0023] In alternative embodiments or in addition, the method may be intended and configured for determining other abnormal combustion conditions, i.e., other abnormal combustion conditions other than combustion knock. For example, the method may be configured for detecting at least one of a "no combustion condition," an "incomplete combustion condition," and a "distorted combustion condition" in an operating cycle of at least one cylinder. Specifically, in this document, the term "no combustion condition" may refer to an operating cycle of a cylinder in which no combustion occurs. The term "incomplete combustion condition" may refer to an operating cycle of a cylinder in which the air-fuel mixture present in the associated combustion chamber during the operating cycle of the cylinder is not completely burned, i.e., only a portion of it is burned. Furthermore, the term "distorted combustion condition" may refer to an operating cycle of a cylinder in which combustion does not start at the desired timing, such as a pre-ignition condition. Specifically, Figure 1 The method described in can be extended to further determine pre-ignition conditions.

[0024] Although the method described below is intended to detect a knock condition within a cylinder, the technical features specified below may also be referenced and applied to detecting the other abnormal combustion conditions mentioned above.

[0025] Figure 1An overview of the proposed method for detecting combustion knock in at least one cylinder of an engine is described. When carrying out the method, a plurality of method steps are performed. In the method shown, the steps are performed successively in a given order. However, the method is not limited to this configuration. Instead, individual method steps may optionally be performed in parallel and / or in a different order, where applicable.

[0026] The proposed method can be executed by a control unit of the engine. That is, at least a part of the method steps or all the method steps can be executed by the control unit.

[0027] The method can be iteratively performed during engine operation. That is, the method can be iteratively performed during engine operation. In particular, a single iteration can be initiated or performed at predetermined and / or regular time intervals. Alternatively, the method can be performed continuously, i.e. without pauses between iterations. That is, after completing one iteration, the next iteration is directly performed. According to one configuration of the method, one iteration of the method is performed for each cylinder and each operating cycle of the cylinder. In other words, for each cylinder to be monitored, one iteration of the method is performed for each operating cycle.

[0028] The method starts when the engine is started. That is, when the engine is started, the method proceeds to method step S1. Figure 1 As shown by the return arrow in , each iteration of the method starts from method step S1 and proceeds according to Figure 1 The flow chart described in .

[0029] In step S1, the operating condition of the engine is monitored, in particular, by a control unit. In this step, the control unit can determine and monitor at least one operating parameter of the engine, such as engine speed, engine temperature, etc. To this end, the control unit can obtain a measurement signal from at least one engine sensor.

[0030] In a next step S2, the monitored operating condition is compared with a predetermined operating condition. Specifically, the control unit can determine whether at least one monitored engine operating parameter has reached a predetermined threshold or is within a predetermined range. This step is performed to ensure that the engine operates under predetermined operating conditions, in particular to allow abnormal combustion conditions to be reliably detected before proceeding to the next method step. In other words, when the engine reaches a predetermined operating condition, the method proceeds to the next step S3. According to one embodiment, the engine speed is monitored and the method proceeds to step S3 when the monitored engine speed reaches a predetermined minimum engine speed. If the predetermined operating condition is not reached, the method returns to step S1, thereby starting the next iteration of the method. In other words, once the engine reaches a predetermined operating condition, the detection is activated.

[0031] In the further course of the method, a cylinder-specific analysis is performed. That is, the following method steps S3 to S7 are performed for each cylinder to be monitored. For the sake of simplicity and to avoid any redundancy, the following method steps are described exemplarily in connection with the detection of abnormal combustion in one of a plurality of cylinders of the engine, however, these method steps are correspondingly applicable to the detection of abnormal combustion and are performed for detecting abnormal combustion in other cylinders of the engine.

[0032] In step S3, cylinder-specific measurement data of the associated cylinder is determined based on the measurement signal acquired by at least one vibration sensor. In this step, the raw signal acquired by at least one vibration sensor is processed to extract the information of interest, i.e., the cylinder-specific measurement data, therefrom. In order to acquire the raw signal, i.e., the measurement signal, one or more vibration sensors may be used, which may be distributedly arranged at or in the engine, in particular at the surface of the engine block and / or cylinder head of the engine. At least one vibration sensor is configured to sense vibrations to provide a measurement signal indicating the vibration intensity or vibration amplitude sensed by the vibration sensor over time. Specifically, the vibration sensor may be configured to measure the movement of the engine, i.e., the oscillating movement. For example, the vibration sensor may be provided in the form of an accelerometer. Such an accelerometer may be configured to sense the inertia acting on the test mass provided therein. In this way, the movement or vibration caused by the engine may be converted into an electrical signal, i.e., a measurement signal. The vibration signal thus measured is hereinafter referred to as a "measurement signal" and may constitute the raw signal acquired by the vibration sensor.

[0033] The at least one vibration sensor can be configured to continuously measure and provide a measurement signal, in particular when starting the engine. In other words, during the operation of the engine, the at least one vibration sensor is configured to continuously, i.e. always, acquire and in particular transmit a measurement signal. Once the engine reaches a predetermined operating condition, the measurement signal is considered a qualified signal and is further processed in step S3.

[0034] exist Figure 2 , step S3 of obtaining cylinder-specific measurement data is described in more detail. In general, step S3 aims at performing a signal characterization of a measurement signal acquired by at least one vibration sensor, i.e. a raw signal, in order to extract information of interest. To this end, in a first sub-step 3.1, the measurement signal acquired by at least one vibration sensor is processed, in particular by applying at least one of filtering techniques, time window techniques and signal aggregation techniques. In this case, "filtering" can be applied to eliminate spikes and high-frequency noise in the measurement signal. "Time window" can be applied to associate parts of the measurement signal acquired by a single vibration sensor with a specific cylinder. "Signal aggregation" can be applied to integrate measurement data acquired by multiple vibration sensors.

[0035] In a next sub-step 3.2, cylinder-specific measurement data for each cylinder are determined based on the processed measurement signals. In the configuration shown, the cylinder-specific measurement data are provided in the form of a vibration profile associated with one cylinder. Thus, at least one vibration profile can be associated with each cylinder. In particular, the vibration profile indicates how the measured vibration amplitude or intensity changes over time.

[0036] Although in the illustrated configuration the steps of processing the measurement signals and determining cylinder-specific measurement data are provided as separate sub-steps, in alternative embodiments this may be performed within a single step. In this way, processing of the raw measurement signals may be performed to determine cylinder-specific measurement data, in particular a vibration profile associated with the cylinder.

[0037] Step S3 may be performed by the control unit. In this configuration, the control unit receives raw measurement signals from at least one vibration sensor and determines the measurement data based thereon. Alternatively, step S3 may be performed by another unit of the engine, for example by at least one vibration sensor. In this configuration, the control unit may receive cylinder-specific measurement data from another unit of the engine.

[0038] In a next optional step S4 of the method, an intensity analysis is performed on the cylinder-specific measurement data to determine an intensity level of the cylinder-specific measurement data. By doing so, the intensity of the vibrations occurring in the associated cylinder during engine operation is determined. In particular, the intensity level may indicate a relative intensity of the cylinder-specific measurement data, in particular compared to a reference intensity.

[0039] exist Figure 3 , step S4 of performing the intensity analysis is described in more detail. In a first sub-step S4.1, an intensity value of the cylinder-specific measurement data is obtained. The intensity value may refer to the amplitude of the vibration profile associated with the cylinder. In particular, the intensity value may refer to a maximum value, in particular to the maximum amplitude of the vibration profile within its associated time window. Alternatively, the intensity value may refer to an average value, in particular to the average amplitude of the vibration profile within the associated time window.

[0040] In a next sub-step 4.2, the determined intensity value is compared with at least one threshold value. Based on this comparison, in a sub-step 4.3, the intensity level of the cylinder-specific measurement signal and therefore the intensity level of the vibration associated with the cylinder is determined. In particular, the intensity level can be determined by classifying the cylinder-specific measurement data, in particular the associated cylinder, into one of at least two categories indicating the intensity level of the cylinder-specific measurement data. In the embodiment shown, the cylinder-specific measurement data and therefore the associated cylinder can be classified into one of the following three categories: "in-band", "higher outlier" and "lower outlier". To this end, the determined intensity value of the cylinder-specific measurement data can be compared with a predetermined threshold range. If the determined intensity value is within the threshold range, the measurement data is classified as "in-band". If the determined intensity value is above the predetermined threshold range, the measurement data is classified as "higher outlier". If the determined intensity value is below the predetermined threshold range, the measurement data is classified as "lower outlier".

[0041] Thereafter, the method proceeds to step S5, which refers to a step of classifying the associated cylinders. Specifically, in this step, at least one cylinder-specific characteristic of the associated cylinder is obtained, wherein the cylinder-specific characteristic is determined according to at least one of a structural arrangement and an operating condition of the associated cylinder.

[0042] As mentioned above, in order to determine at least a part of the at least one cylinder-specific characteristic, the structural arrangement of the associated cylinder, i.e. for which the cylinder-specific characteristic is to be obtained, may be taken into account. For this purpose, stimulation techniques may be used, in particular computer simulations, such as structural or steady-state stiffness simulations, for example by applying the finite element method. In other words, the at least one cylinder-specific characteristic may be determined using computer simulations.

[0043] Alternatively or additionally, at least one cylinder-specific characteristic can be determined by taking into account investigations on the engine during operation of the engine. Thus, at least a part of the at least one cylinder-specific characteristic can be determined taking into account the operating conditions of the engine, in particular the cylinders. For this purpose, the results of the investigations on the engine can be taken into account. The results of the investigations on the engine can be derived based on test runs performed on the engine or on a reference engine. Alternatively or additionally, the results of the investigations on the engine can be obtained during the expected use of the engine, in particular during its application-specific use. For this purpose, for example, the strength analysis performed in step S4, i.e. the strength level of the measurement data associated with the cylinders, can be taken into account.

[0044] According to one embodiment, the obtained at least one cylinder-specific characteristic may indicate that the associated cylinder is at least one of: "prone to valve closing noise", "prone to piston knocking noise", "prone to knock", "subject to transmission asymmetry", "prone to pre-ignition".

[0045] In the configuration shown, when step S5 is performed, the associated cylinder is classified into only one or at least one of the following classification categories: "prone to valve closing noise", "prone to piston knocking noise", "prone to knocking", "subject to transmission asymmetry", "prone to pre-ignition" and "unclassified". In this case, classification into at least one of these classification categories constitutes a cylinder-specific characteristic.

[0046] In order to determine whether the associated cylinder is classified as "prone to valve closing noise", a structural analysis, in particular a computer-implemented structural simulation, can be performed. By doing so, it can be determined which cylinders and which time windows during their operating cycle may be affected by valve closing noise. In order to determine whether the associated cylinder is classified as "prone to valve closing noise", a strength analysis of cylinder-specific measurement data can be performed, in particular in a predetermined time window. In order to determine whether the associated cylinder is classified as "prone to knock", computer-implemented simulations and / or investigation results on the engine can be taken into account. In order to determine whether the associated cylinder is classified as "transmission asymmetry", a steady-state structural simulation and / or a stiffness analysis can be performed. In order to determine whether the associated cylinder is classified as "prone to pre-ignition", a strength analysis of cylinder-specific measurement data can be performed, in particular in a predetermined time window. This analysis can also be used to determine the pre-ignition condition as an abnormal combustion condition. Any cylinder that does not belong to one of the above categories or a combination of the above categories can be classified as "unclassified".

[0047] In a next step S6 , a cylinder specific detection profile, also referred to as abnormal combustion detection profile or knock detection profile, is defined depending on at least one cylinder characteristic of the associated cylinder determined in step S5 and optionally on the intensity level determined in step S4 .

[0048] In the context of the present invention, the term "detection configuration" refers to a configuration that specifies how to perform the detection of abnormal combustion, in particular based on which detection procedure and detection parameters. Therefore, the detection configuration is decisive for how and under what circumstances the abnormal combustion condition in the associated cylinder is detected. Specifically, the detection configuration may include or specify a detection time window, a detection method, and a detection condition.

[0049] In the context of the present invention, the term "detection time window", which may also be referred to as "detection time interval", refers to a time interval, in particular a time interval within an operating cycle of an associated cylinder, wherein cylinder-specific measurement data is to be analyzed to determine whether an abnormal combustion, in particular a knock event, has occurred during the operation of the associated cylinder. In other words, the detection time window is a time window of interest, wherein the cylinder-specific measurement data associated with the time window is to be analyzed to detect and identify combustion knock. That is, the detection time window indicates at least a portion or a subset of the cylinder-specific measurement data to be analyzed to detect abnormal combustion.

[0050] The detection time window may correspond to or may exclude at least one of a core combustion window, a pre-ignition window, a valve closing noise window, a piston knock noise window, and a global window. These time windows refer to a portion of an operating cycle of an associated cylinder.

[0051] Specifically, the term "core combustion window" may refer to a time window in which combustion occurs in a combustion chamber, in particular a main combustion chamber into which a pre-combustion chamber extends. The term "pre-combustion window" may refer to a time window in an operating cycle in which pre-combustion, in particular in a pre-combustion chamber, occurs. The term "valve closing noise window" may refer to a time window in an operating cycle in which valve closing noise exists. More specifically, the valve closing noise window may refer to a time window in which air and / or fuel are supplied to the cylinder. Alternatively or additionally, the valve closing noise window may refer to a time window in which exhaust gas is discharged from the cylinder. The term "piston knocking noise window" may refer to a time window in an operating cycle in which piston knocking noise exists. The term "global window" may refer to a time window in an operating cycle that includes a core combustion window. Therefore, the core combustion window is smaller than the global window. In addition, the global window may at least partially include at least one of a pre-ignition window, a valve closing noise window, and a piston knocking noise window.

[0052] As mentioned above, the detection configuration also specifies a detection method, which may also be referred to as an abnormal combustion detection method or a combustion knock detection method. In the context of the present invention, a detection method defines a detection procedure that specifies how to process cylinder-specific measurement data, in particular data within a detection time window, to detect abnormal combustion. For example, the detection method may be selected from at least one of a maximum intensity method, an integral intensity method, and a difference monitoring method.

[0053] According to the maximum intensity method, the amplitude maximum value of cylinder-specific measurement data within the detection window, in particular the maximum value of vibration intensity, can be derived and then compared with a predetermined threshold to determine whether abnormal combustion, in particular a knock event, has occurred in the cylinder.

[0054] According to the integrated intensity method, the amplitude integral value of the cylinder-specific measurement data within the detection window, in particular the integral value of the vibration intensity, can be derived and then compared with a predetermined threshold to determine whether abnormal combustion, in particular a knock event, has occurred in the cylinder.

[0055] According to the difference monitoring method, the difference between the maximum value of the amplitude of the cylinder-specific measurement data within the detection window, in particular the maximum value of the vibration intensity and the average value across a number of previous detection windows, i.e. with reference to previous operating cycles, can be calculated. The derived difference value can then be compared with a threshold value to detect abnormal combustion conditions.

[0056] As mentioned above, the detection configuration further specifies a detection condition, which refers to a predefined condition, in particular with respect to the obtained and in particular processed cylinder-specific measurement data, which indicates an abnormal combustion condition in the associated cylinder. In other words, the detection condition may define a threshold value to be compared with the cylinder-specific measurement data to detect the abnormal combustion condition. In particular, the detection condition may define a detection threshold value, in particular a threshold value used in the above-mentioned detection method. The detection condition, in particular the detection threshold value, may be a cylinder-specific condition or value or a global condition or value, i.e. applicable to all cylinders of the engine.

[0057] In the illustrated configuration, the definition of each detection time window, detection method and detection condition is based on at least one cylinder characteristic of the associated cylinder determined in step S5 and optionally on the intensity level determined in step S4.

[0058] In accordance with Figure 1 In the method, steps S5 and S6 are performed after method step S4. However, the proposed method is not limited to this configuration. Alternatively, steps S5 and S6 can be performed before method step S4 or in parallel with method step S4.

[0059] Furthermore, in the method shown, the determination of the cylinder-specific characteristics and the determination of the detection configuration may be at least partially performed before the method is performed. Then, when the method is performed, the results of these determinations are obtained in steps S5 and S6. For example, at least a portion of the determination of the cylinder-specific characteristics may be determined before the engine is started or initially operated.

[0060] In a next step S7 , the control unit analyses the cylinder-specific measurement data based on the associated detection configuration to determine abnormal combustion conditions in the associated cylinder, in particular to determine whether the associated cylinder is subject to a knock event.

[0061] It is obvious to those skilled in the art that these embodiments and projects only describe the examples of multiple possibilities. Therefore, the embodiments shown here should not be construed as forming the limitations of these features and configurations. Any possible combination and configuration of the described features can be selected according to the scope of the present invention. This is especially the case with the following optional features, which can be combined with some or all of the embodiments, projects and / or features mentioned above in any technically feasible combination.

[0062] Therefore, a method for detecting abnormal combustion, in particular combustion knock and / or pre-ignition, in at least one cylinder of an internal combustion engine is proposed. The method may comprise: a step of determining cylinder-specific measurement data for each of the at least one cylinder based on measurement signals acquired by at least one vibration sensor; a step of obtaining a cylinder-specific detection configuration for each of the at least one cylinder; and, for each of the at least one cylinder, a step of analyzing the cylinder-specific measurement data based on the associated detection configuration to detect abnormal combustion conditions.

[0063] In the context of the present invention, it has been found that due to the multiple dependencies and significant variations of cylinder characteristics within an engine, improved detection can be provided when cylinder-specific characteristics are taken into account. Since in the proposed method a cylinder-specific detection configuration is defined for each cylinder to be monitored, structural and operational differences between different cylinders of the engine are taken into account. This allows for a more reliable detection of abnormal combustion conditions within a single cylinder.

[0064] The method may further comprise the step of monitoring the engine operating conditions, wherein when the engine reaches a predetermined engine condition, the method in particular proceeds to the step of determining cylinder specific measurement data. Specifically, in the step of monitoring the operating conditions, the engine speed of the engine may be monitored, and when the monitored engine speed reaches a predetermined minimum engine speed, the method may proceed to subsequent steps.

[0065] Alternatively or additionally, the step of determining cylinder specific measurement data may comprise the sub-step of processing the measurement signal acquired by the at least one vibration sensor by applying at least one of filtering and time windowing.Alternatively or additionally, the step of determining cylinder specific measurement data may comprise the sub-step of determining a cylinder vibration profile for each of the at least one cylinder.

[0066] In a further development, the method may further comprise the step of determining an intensity level of the cylinder specific measurement data. Optionally, the step of determining the intensity level may comprise the sub-step of determining a maximum or average intensity value of the cylinder specific measurement data and the sub-step of comparing the determined intensity value with at least one threshold value.

[0067] In a further development, the method may further comprise the step of obtaining at least one cylinder characteristic of each of the at least one cylinder. Optionally, the cylinder characteristic may be determined based on at least one of a structural arrangement and an operating condition of the associated cylinder. Optionally, the detection configuration for each of the at least one cylinder may be determined based on the associated cylinder characteristic.

[0068] Additionally, cylinder-specific characteristics may be determined using computer simulations and / or using on-engine investigations during engine operation.

[0069] In a further development, the cylinder-specific characteristic may indicate that the associated cylinder is prone to at least one of: valve closing noise, piston slapping noise and knocking.

[0070] The cylinder-specific detection configuration may also be defined according to the strength level of the associated cylinder-specific measurement data.

[0071] In a further development, the cylinder-specific detection configuration may specify at least one of a detection time window, a detection method, and a detection condition indicating a portion of the measurement data to be analyzed. In particular, the detection time window may correspond to at least one of a pre-ignition window, a core combustion window, a valve closing noise window, and a piston knock noise window within an associated cylinder operating cycle. Alternatively or additionally, the detection condition may define a threshold value to be compared with the cylinder-specific measurement data to detect an abnormal combustion condition. Alternatively or additionally, at least one of the detection time window, the detection method, and the detection condition is defined according to an associated cylinder characteristic.

[0072] Furthermore, a control unit of an internal combustion engine for detecting abnormal combustion, in particular combustion knock and / or pre-ignition, in at least one cylinder may be provided. The control unit may be configured such that the control unit is configured to determine cylinder-specific measurement data for each of the at least one cylinder based on measurement signals acquired by the at least one vibration sensor, to obtain a cylinder-specific detection configuration for each of the at least one cylinder, and to analyze the cylinder-specific measurement data for each of the at least one cylinder based on the associated detection configuration to detect abnormal combustion conditions.

[0073] Industrial Applicability

[0074] refer to Figure 1 With the accompanying description, a method and a control unit for detecting abnormal combustion in at least one cylinder of an internal combustion engine are proposed. The method and the control unit as described above are suitable for an internal combustion engine, for example, which is arranged as a stationary gas engine. The proposed method can be performed in a conventional internal combustion engine or used for a conventional internal combustion engine. In addition, the proposed control unit can replace a conventional control unit and can be used as a replacement or improved component.

Claims

1. A method for detecting abnormal combustion, in particular combustion knock or pre-ignition, in at least one cylinder of an internal combustion engine, comprising: - a step of determining cylinder-specific measurement data for each of at least one cylinder based on the measurement signals acquired by at least one vibration sensor; - a step of obtaining a cylinder-specific detection configuration for each of at least one cylinder; as well as - For each of at least one cylinder, a step of analyzing said cylinder-specific measurement data based on said associated detection configuration to detect abnormal combustion conditions.

2. The method according to claim 1, further comprising the step of monitoring the operating condition of the engine, wherein: The method continues when the engine reaches predetermined engine conditions.

3. The method according to claim 2, wherein: In the step of monitoring operating conditions, an engine speed of the engine is monitored, and the method continues when the monitored engine speed reaches a predetermined minimum engine speed.

4. The method according to any one of claims 1 to 3, wherein: Said step of determining cylinder-specific measurement data comprises the sub-step of processing said measurement signal acquired by said at least one vibration sensor by applying at least one of filtering and time windowing.

5. The method according to any one of claims 1 to 4, wherein: Said step of determining cylinder-specific measurement data comprises the sub-step of determining a vibration profile for each of said at least one cylinder.

6. The method according to any one of claims 1 to 5, further comprising the step of determining a strength level of the cylinder-specific measurement data, wherein: In particular, the step of determining the intensity level comprises the sub-step of determining a maximum or average intensity value of the cylinder-specific measurement data and the sub-step of comparing the determined intensity value with at least one threshold value.

7. The method according to any one of claims 1 to 6, further comprising The step of obtaining at least one cylinder characteristic of each of at least one cylinder, wherein The cylinder characteristic is determined based on at least one of a structural arrangement and an operating condition of the associated cylinder, and wherein the detection configuration of each of the at least one cylinder is determined based on the associated cylinder characteristic.

8. The method according to claim 7, wherein: The cylinder-specific characteristics are determined by using computer simulations or by using investigations on the engine during engine operation.

9. The method according to claim 7 or 8, wherein: The cylinder-specific characteristic indicates that the associated cylinder is susceptible to at least one of: valve closing noise, piston slap noise, and knock.

10. The method according to any one of claims 6 to 9, wherein: The cylinder-specific detection configuration may also be defined depending on the intensity level of the associated cylinder-specific measurement data.

11. The method according to any one of claims 1 to 10, wherein: The cylinder-specific detection profile specifies at least one of a detection time window, a detection method, and an abnormal combustion detection condition indicating a portion of the measurement data to be analyzed.

12. The method according to any one of claims 1 to 11, wherein: The detection time window corresponds to at least one of a pre-ignition window, a core combustion window, a valve closing noise window, and a piston knock noise window within the associated cylinder operating cycle.

13. The method according to claim 12, wherein: The detection condition defines a threshold value to be compared to the cylinder specific measurement data to detect the abnormal combustion condition.

14. The method according to any one of claims 11 to 13, wherein: At least one of the detection time window, the detection method, and the abnormal combustion detection condition is defined according to the associated cylinder characteristic.

15. A control unit for an internal combustion engine, for detecting abnormal combustion in at least one cylinder, in particular combustion knock and / or pre-ignition conditions, wherein: The control unit is configured to: - determining cylinder-specific measurement data for each of the at least one cylinder based on measurement signals acquired by at least one vibration sensor; - obtaining a cylinder-specific detection configuration for each of the at least one cylinder; as well as - for analyzing, for each of at least one cylinder, said cylinder-specific measurement data based on said associated detection configuration to detect abnormal combustion conditions.

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