CN114441179B - Engine combustion non-uniformity detection system and detection method - Google Patents
Engine combustion non-uniformity detection system and detection method Download PDFInfo
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Abstract
The application relates to an engine combustion non-uniformity detection system and a detection method, wherein the engine combustion non-uniformity detection system comprises: the vibration sensor is arranged on a cylinder body of the engine and is used for detecting vibration signals of the cylinder body; the pipe clamp sensor is arranged on a high-pressure oil pipe of the engine and is used for detecting a pulse signal of the high-pressure oil pipe; the data acquisition card is respectively and electrically connected with the vibration sensor and the pipe clamp sensor; and the controller is electrically connected with the data acquisition card and judges whether the engine burns unevenly or not according to the vibration signals and the high-pressure oil pipe pulse signals acquired by the data acquisition card. According to the engine combustion non-uniformity detection system provided by the application, the fault detection of the engine cylinder combustion non-uniformity is completed by adopting a signal processing means according to the signals detected by the vibration sensor and the pipe clamp sensor.
Description
Technical Field
The application relates to the technical field of engines, in particular to an engine combustion non-uniformity detection system and a detection method.
Background
This section provides merely background information related to the present disclosure and is not necessarily prior art.
The engine is used as a power component of a whole vehicle system, the uniform combustion of each cylinder of the engine is the basis of the stable operation of the whole vehicle, and particularly, the insufficient combustion or the non-combustion of fuel in the cylinder is caused by the influence of abnormal factors such as the fault of an oil injector, the calibration of performance and the like in the actual operation process of a diesel engine, so that the engine has uneven combustion or fire fault, and further, the problems of exceeding standard emission, the decline of output torque and output power, the deterioration of vibration noise, abnormal sound and the like of the diesel engine are caused.
Therefore, it is necessary to detect the combustion uniformity of the engine, and the combustion uniformity of each cylinder is specifically expressed as the uniformity of the cylinder pressures of each cylinder, and the cylinder pressure detection is the most accurate method, but it is limited by the fact that the cylinder pressure sensor has high cost and poor reliability, and the like, and cannot be popularized. The fluctuation and torsional vibration of the rotating speed can better diagnose the fire failure of the diesel engine, but when a certain cylinder has insufficient combustion (no fire), the cylinder pressure of the cylinder changes little, the influence on the fluctuation of the rotating speed is little, and the detection of the non-uniformity of the combustion by the rotating speed signal can fail.
The existing detection of uneven combustion or fire faults of the engine has the defects that:
1) The detection of the combustion non-uniformity based on the cylinder pressure signal belongs to an invasive detection means, and the detection mode is limited by the high cost, poor reliability and other factors of the cylinder pressure sensor, which are only limited to the use in a laboratory, so that the detection mode is difficult to popularize;
2) The effect of the engine fire diagnosis (obvious pressure difference of each cylinder) based on the rotation speed signal is better, but the effect of detecting the cylinder pressure non-uniformity (the cylinder pressure difference of each cylinder is not obvious) in the non-fire state is poorer, the detection precision can be improved by a machine learning method and the like, but the machine learning method is completely dependent on the acquired test data, lacks the research of a characteristic mechanism, and the synthesized machine learning algorithm is only responsible for the test data, is easy to be influenced by variable rotation speed, variable working condition and road load fluctuation to cause unstable detection, and meanwhile, the signal wire of the external tee-joint rotation speed sensor is required to easily interfere the ECU signal;
3) The existing detection means based on vibration signals needs a plurality of sensors to acquire phase information and multi-cylinder vibration signals for detection, and is high in cost and low in efficiency.
Disclosure of Invention
The application provides a system and a method for detecting engine combustion non-uniformity, which aim to at least solve the technical problem that the existing vehicle is complex in detecting the engine combustion non-uniformity, and the aim is realized by the following technical scheme:
a first aspect of the present application provides an engine combustion unevenness detecting system, comprising: the vibration sensor is arranged on a cylinder body of the engine and is used for detecting vibration signals of the cylinder body; the pipe clamp sensor is arranged on a high-pressure oil pipe of the engine and is used for detecting a pulse signal of the high-pressure oil pipe; the data acquisition card is respectively and electrically connected with the vibration sensor and the pipe clamp sensor; and the controller is electrically connected with the computer readable storage medium of the data acquisition card and judges whether the engine burns unevenly or not according to the vibration signal and the high-pressure oil pipe pulse signal acquired by the data acquisition card.
According to the engine combustion non-uniformity detection system provided by the application, the fault detection of the engine cylinder combustion non-uniformity is completed by adopting a signal processing means according to the signals detected by the vibration sensor and the pipe clamp sensor. Compared with the existing diagnosis method, the method has the advantages of low cost, high efficiency and high precision. The method solves the problems of high cost, poor reliability (the sensor is easy to fail) and the like of the invasive detection means based on the cylinder pressure signal, and solves the problems of high cost, low efficiency and poor precision of the existing detection means based on the vibration signal.
Further, a vibration sensor is provided at an upper edge of the cylinder block and at an intermediate position between the plurality of cylinder blocks of the engine, the vibration sensor detecting vibration signals of the plurality of cylinder blocks simultaneously.
A second aspect of the present application provides an engine combustion unevenness detecting method, which is implemented according to the engine combustion unevenness detecting system of the first aspect of the present application, the engine combustion unevenness detecting method including the steps of: acquiring a vibration signal X1 of a cylinder body under a working condition to be detected and a pulse signal X2 of a high-pressure oil pipe; acquiring a plurality of vibration signals X1 and generating signals X3 in a plurality of stroke cycles of a cylinder block, and acquiring a plurality of high-pressure oil pipe pulse signals X2 and generating signals X4; correcting the oil injection advance angle of the cylinder body according to the signal X4, and then acquiring the top dead center position a of the cylinder body; processing the signal X3 according to the VMD algorithm to obtain a signal X5, and acquiring combustion excitation energy h of the cylinder block corresponding to the top dead center position a according to the signal X5; and analyzing a plurality of combustion excitation energies h of a plurality of cylinder blocks of the engine, and judging whether the cylinder blocks of the engine burn unevenly or not according to the combustion excitation energies h.
Further, processing the signal X3 according to the VMD algorithm to obtain a signal X5, and obtaining combustion excitation energy h of the cylinder block corresponding to the top dead center position a according to the signal X5 includes: acquiring mechanical excitation energy a of a cylinder body of an engine in an unburned state under a test working condition; acquiring a vibration signal X3 of the cylinder body of the engine under the working condition to be detected, and calculating excitation energy A of the cylinder body according to the vibration signal X3; and (3) subtracting the mechanical excitation energy a from the excitation energy A to obtain combustion excitation energy h of the cylinder body corresponding to the top dead center position a under the working condition to be detected.
Further, the obtaining the mechanical excitation energy a of the cylinder block under the unburned state of the test working condition specifically comprises: the engine is controlled to stably run in a reverse towing working condition under a test state; recording ignition phase information under different rotating speeds and different air inflow and vibration signals of the cylinder body; and calculating the mechanical excitation energy a of the cylinder body corresponding to the top dead center position a under the test working condition according to the ignition phase information and the vibration signal of the cylinder body.
Further, recording ignition phase information under different rotational speeds and different air inflow amounts, and vibration signals of the cylinder block specifically includes: the air inflow of the engine is controlled by adjusting the opening degree of the air inflow throttle valve, and the ignition phases under different rotating speeds and different air inflow flows and vibration signals of the cylinder body are recorded. Specifically, the intake throttle valve may control the valve opening by an ECU signal, thereby adjusting the intake air amount of the engine to reduce emissions.
Further, processing the signal X3 according to the VMD algorithm to obtain a signal X5, and obtaining combustion excitation energy h of the cylinder block corresponding to the top dead center position a according to the signal X5 further includes: decomposing the vibration signal X3 according to a VMD algorithm, and obtaining time domain signals ui separated by each IMF mode after VMD decomposition; confirming ignition phase information according to signals X4 generated by a plurality of high-pressure oil pipe pulse signals X2; combustion excitation energy h is generated from the respective IMF modal components and firing phase information.
Further, the obtaining the time domain signal ui separated by each IMF mode after the vibration signal X3 is decomposed according to the VMD algorithm and VMD decomposition further includes: calculating the self-power spectrum of each IMF modal component, and acquiring the center frequency Fi of each IMF modal component; inquiring whether each center frequency Fi contains the engine ignition frequency, and readjusting VMD algorithm parameters if the center frequency Fi does not contain the engine ignition frequency until each IMF modal component containing the engine ignition frequency is obtained.
Further, determining whether the plurality of cylinder blocks of the engine are unevenly combusted based on the plurality of combustion excitation energies h specifically includes: comparing two combustion excitation energies h of two adjacent cylinder blocks; and judging that the combustion of two adjacent cylinder blocks of the engine is uneven according to the fact that the difference value of the two combustion excitation energies h is larger than the preset difference value.
Further, according to the difference between the two combustion excitation energies h being greater than the preset difference, determining that the combustion of the two adjacent cylinder blocks of the engine is uneven further includes: according to the fact that the combustion of two adjacent cylinder blocks is uneven, and the combustion excitation energy h of the front cylinder block is larger than the combustion excitation energy h of the rear cylinder block, the cylinder pressure of the front cylinder block is judged to be increased, and the cylinder pressure of the rear cylinder block is judged to be reduced; and according to the fact that the combustion of the two adjacent cylinder blocks is uneven and the combustion excitation energy h of the front cylinder block is smaller than the combustion excitation energy h of the rear cylinder block, determining that the cylinder pressure of the front cylinder block is reduced and the cylinder pressure of the rear cylinder block is increased.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the application. Also, like reference numerals are used to designate like parts throughout the figures. In the drawings:
FIG. 1 is a schematic diagram of an engine combustion non-uniformity detection system according to an embodiment of the present application;
FIG. 2 is a flow chart of a method of detecting engine combustion non-uniformity according to an embodiment of the present application;
FIG. 3 is a flow chart of a method for detecting engine combustion non-uniformity according to another embodiment of the present application;
FIG. 4 is a flowchart of a method of detecting engine combustion non-uniformity according to yet another embodiment of the present application;
FIG. 5 is a graph of the variation of the activation energy of each cylinder in a reduced cylinder pressure state according to one embodiment of the present application;
FIG. 6 is a graph of relative change in actuation energy for each cylinder in accordance with one embodiment of the present application;
wherein,
10. an engine; 11. a 1-cylinder; 12. 2, a cylinder; 13. 3 cylinders; 14. a 4-cylinder;
20. a vibration sensor;
30. a pipe clamp sensor;
40. a data acquisition card;
50. and an upper computer.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
It is to be understood that the terminology used herein is for the purpose of describing particular example embodiments only, and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," and "having" are inclusive and therefore specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof.
Although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "first," "second," and "third," and other numerical terms, when used herein, do not imply a sequence or order unless clearly indicated by the context. In addition, in the description of the present application, unless explicitly stated and limited otherwise, the terms "disposed" and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be directly connected or indirectly connected through an intermediate medium. The specific meaning of the above terms in the present application can be understood by those skilled in the art according to the specific circumstances.
For ease of description, spatially relative terms, such as "upper," "inner," "proximal," and the like, may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" or "over" the other elements or features. Thus, the example term "below … …" may include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions) and the spatially relative relationship descriptors used herein interpreted accordingly.
FIG. 1 is a schematic diagram showing the installation and use of a combustion non-uniformity detection system for an engine 10 according to an embodiment of the present application:
1) The vibration sensor 20 is mounted at the upper edge position of the cylinder block, the vibration sensor 20 can be mounted at the upper edge position of the cylinder block according to the whole machine arrangement of the engine 10, a detection point on the cylinder block is most sensitive to the induction of combustion excitation, the vibration sensor 20 cannot be placed at a cylinder cover position, because the detection point on a cylinder cover is greatly influenced by the interference of valve opening and seating energy, there is a risk of flooding the combustion excitation energy, the vibration sensor 20 is optionally mounted at an intermediate cylinder position of the engine 10, for example, for a 4-cylinder diesel engine, the vibration sensor 20 is mounted at a position between a 2-cylinder 12 and a 3-cylinder 13, and for a 6-cylinder engine, the vibration sensor 20 is mounted at a position between the 3-cylinder 13 and the 4-cylinder 14;
2) The pipe clamp sensor 30 is used for detecting the ignition phase of the engine 10 through a high-pressure oil pipe of the engine 10, determining the ignition phase information and compression top dead center information of a certain cylinder through a pulse signal of the high-pressure oil pipe, optionally collecting cylinder pressure oil pipe information of the 1 cylinder 11, and optionally collecting the cylinder pressure oil pipe information of the 1 cylinder, wherein the pipe clamp sensor 30 is a vibration sensor, can be used for testing oil supply pulses of the high-pressure oil pipe, does not require the detection frequency of the pipe clamp sensor 30, has a pipe clamp structure, and can detect the ignition phase of a single cylinder through the pulse signal of the high-pressure oil pipe detected by the pipe clamp sensor 30;
3) The data acquisition card 40 is used for acquiring vibration signals of the cylinder block, and when the engine 10 stably runs under a certain working condition, the data acquisition card 40 is used for acquiring pulse signals of the high-pressure oil pipe and vibration signals of the cylinder block of the engine 10;
4) The controller of the upper computer 50 receives the vibration signal of the cylinder block and the high-pressure oil pipe pulse signal, stores them in a computer-readable storage medium, and recognizes the combustion unevenness of each cylinder by the combustion unevenness algorithm of each cylinder.
Specifically, the high-pressure oil pipe includes a fuel injector wire harness, the pipe clamp sensor 30 includes but is not limited to CAN communication through ECU signal connection, the pipe clamp sensor 30 detects the fuel injector wire harness of the engine through the current clamp, and the vibration sensor 20 detects vibration signals of the cylinder block, the cylinder head cover, and the like in combination with signal processing, machine learning, a deep learning algorithm, and the like to perform key phase (determine phase information of ignition of each cylinder).
As shown in fig. 2, a method for detecting combustion unevenness of an engine 10 is provided, wherein the method for detecting combustion unevenness of an engine 10 is implemented by the system for detecting combustion unevenness of an engine 10 according to the first aspect of the present application, and the main idea of the flow for detecting combustion unevenness of each cylinder of an engine 10 is to identify a combustion unevenness failure of each cylinder by using a vibration signal of a single cycle (a crankshaft of the engine 10 rotates two times, each cylinder of the engine 10 is ignited once for one cycle), and to determine the combustion unevenness failure of each cylinder by taking an average of detection results of a plurality of cycles, wherein the method comprises the main steps of:
s10, acquiring a vibration signal X1 of a cylinder body under a working condition to be detected and a pulse signal X2 of a high-pressure oil pipe;
s20, acquiring a plurality of vibration signals X1 and generating signals X3 in a plurality of stroke cycles of the cylinder block, and acquiring a plurality of high-pressure oil pipe pulse signals X2 and generating signals X4;
s30, correcting the oil injection advance angle of the cylinder body according to the signal X4, and then acquiring the top dead center position a of the cylinder body;
s40, processing the signal X3 according to the VMD algorithm to obtain a signal X5, and acquiring combustion excitation energy h of the cylinder block corresponding to the top dead center position a according to the signal X5;
s50, analyzing a plurality of combustion excitation energies h of a plurality of cylinder blocks of the engine 10, and judging whether the cylinder blocks of the engine 10 are unevenly combusted according to the combustion excitation energies h.
As shown in fig. 3, combustion excitation energy of each cylinder is extracted by a VMD algorithm, vibration signal X3 is required to be subjected to VMD decomposition, time domain signal ui separated by each IMF mode is obtained, ignition phase information is confirmed from signal X4 generated by a plurality of high-pressure oil pipe pulse signals X2, and combustion excitation energy h is generated from each IMF mode component and ignition phase information.
Specifically, the method for detecting the non-uniformity of each cylinder provided by the embodiment of the application mainly extracts the combustion excitation energy of each cylinder after the decomposition of the VMD so as to judge the combustion non-uniformity of each cylinder, and the flow of the algorithm for detecting the non-uniformity of the cylinder pressure of each cylinder is shown in fig. 4, and the step S40 specifically comprises the following steps:
1) Acquiring mechanical excitation energy a of a cylinder block of engine 10 in an unburned state under test conditions, wherein the mechanical excitation energy a comprises a for a 4-cylinder diesel engine 1 、a 2 、a 3 、a 4 ；
2) Acquiring a vibration signal X3 of the cylinder block of the engine 10 under the working condition to be detected, and calculating excitation energy A of the cylinder block according to the vibration signal X3, wherein the excitation energy A comprises A for a 4-cylinder diesel engine 1 、A 2 、A 3 、A 4 ；
3) Calculating excitation energy A minus mechanical excitation energy a to obtain combustion excitation energy h of the cylinder block corresponding to the top dead center position a under the working condition to be detected, wherein the combustion excitation energy h comprises h for a 4-cylinder diesel engine 1 、h 2 、h 3 、h 4 ；
Wherein the mechanical excitation energy obtaining step of each cylinder in the unburned state in the laboratory state includes:
1) After the engine 10 is stably operated at a certain rotating speed and fully warmed up, a rack control mode of the engine 10 is adjusted, the dynamometer drags the engine 10 to rotate, the engine 10 is stably operated under a reverse dragging working condition, the air inlet flow of the current working condition is recorded, ignition phase information of the engine 10 is collected, oil pipes in the reverse dragging working condition are not supplied with oil, and ignition phase signals and vibration signals of a cylinder body can be collected through single-cylinder pressure sensor information;
2) Adjusting ECU data, controlling the air inflow of the engine 10 by adjusting the opening degree of an air inlet throttle valve, continuously reducing the in-cylinder pressure along with the reduction of the opening degree of the air inlet throttle valve, continuously reducing the mechanical excitation energy of each cylinder, and recording the rotation speed, the ignition phase of the engine 10 under different air inlet flow rates and the vibration signals of a cylinder body;
3) Repeating the steps, and recording the ignition phase information of the engine 10 and the vibration signals of the cylinder body under different rotation speeds and different air inflow;
4) The mechanical excitation energy of each cylinder is extracted from the phase information of the engine 10 and the vibration signal of the cylinder block.
Further, the step S30 specifically includes: the ignition phase information can be used for obtaining the compression top dead center phase information of each cylinder, the mechanical excitation energy calculating method is an integrating method, and an integrating interval is 20 degrees before and after the compression top dead center of each cylinder (different types can be adjusted). The method comprises the steps of carrying out average processing on mechanical excitation energy of a plurality of periods to obtain excitation energy of each cylinder, and obtaining a data table of the mechanical excitation energy of each cylinder under different rotation speeds and different air inlet flow rates.
In a state of the to-be-detected condition of actual use of the engine 10, the method of detecting the nonuniformity of each cylinder:
1) Acquiring pulse signal X of high-pressure oil pipe 4 Vibration signal X of cylinder block 3 For vibration signal X 3 Performing VMD (Variational mode decomposition) decomposition to obtain time domain signals ui of each IMF (Intrinsic Mode Functions, meaning modal components) modal separation, calculating the self-power spectrum of each IMF modal component, and obtaining the center frequency Fi of each component;
2) It is checked whether Fi contains the ignition frequency of engine 10 and if it does not contain the ignition frequency of engine 10, the VMD parameters need to be readjusted until IMF components containing the ignition frequency of engine 10 are obtained. As shown in fig. 5, the IMF mode component of the ignition frequency of the engine 10 is contained in the state that the cylinder pressure of the 2 cylinder 12 is reduced by 0.5Mpa, the vibration response of the ignition combustion moment of the 2 cylinder 12 measured by the vibration sensor 20 is obviously reduced in the working condition that the cylinder pressure of the 2 cylinder 12 is reduced, and meanwhile, the cylinder pressure of the ignition combustion moment of the 1 cylinder 11 is increased to a certain extent, so that the effectiveness of the combustion non-uniformity fault detection method by using the vibration signal is proved;
3) Based on the ignition phase information detected by the pipe clamp sensor 30, the excitation energy corresponding to the compression top dead center for each cylinder is determined. Since the vibration peak information of the high-pressure oil pipe is not 1 compression top dead center of the cylinder 11 at the oil supply time, the ignition phase information needs to be corrected, and the ignition phase information corresponding to the compression top dead center of each cylinder after the correction is obtained. The excitation energy calculation method is an integration method, and the integration interval is 20 degrees before and after the compression top dead center of each cylinder (different models can be adjusted and the calculation method is consistent with the calculation method in an unburned state). The method comprises the steps of carrying out average value processing on excitation energy of a plurality of periods to obtain excitation energy of each cylinder, wherein energy losses of different degrees exist at positions where the excitation energy of different cylinders is transmitted to a detection point of the sensor, so that a simulation or test means is required to be adopted to obtain a transfer function of the excitation energy of each cylinder transmitted to the detection point of the sensor, and the transfer function is taken as a reference to correct the excitation energy of each cylinder;
4) Subtracting the mechanical excitation energy of each cylinder in an unburned state from the excitation energy of each cylinder in step 3), and obtaining the combustion excitation energy of each cylinder;
5) The method comprises the steps of carrying out non-uniformity diagnosis according to combustion excitation energy of each cylinder, carrying out cylinder pressure non-uniformity evaluation by solving methods such as variance, peak-to-valley value and the like, and carrying out non-uniformity evaluation by using relative excitation energy difference values of adjacent cylinders according to the embodiment of the application: calculating the difference in activation energy variation of adjacent cylinders (taking the firing order 1-3-4-2 of the 4-cylinder engine 10 as an example, p13 is represented by 1-cylinder 11 combustion activation energy minus 3-cylinder 13 combustion activation energy, p13=h1-h 3, p34=h3-h 4, p42=h4-h 2, p21=h2-h 1), as shown in fig. 6, the relative activation energy variation of adjacent cylinders in three different states, 4 data in each state corresponding to p13, p34, p42, p21, respectively;
according to an embodiment of the present application, two combustion excitation energies h of adjacent two cylinder blocks are compared; if the difference between the two combustion excitation energies h is greater than the preset difference, it is determined that the combustion of the two adjacent cylinder blocks of the engine 10 is uneven, and if the combustion excitation energy h of the front cylinder block is greater than the combustion excitation energy h of the rear cylinder block, it is determined that the cylinder pressure of the front cylinder block is increased and the cylinder pressure of the rear cylinder block is decreased; and according to the fact that the combustion of the two adjacent cylinder blocks is uneven and the combustion excitation energy h of the front cylinder block is smaller than the combustion excitation energy h of the rear cylinder block, determining that the cylinder pressure of the front cylinder block is reduced and the cylinder pressure of the rear cylinder block is increased.
Taking fig. 6 as an example, the non-uniformity fault determination method is described:
a. comparing two combustion excitation energies h of adjacent two cylinder blocks, and then extracting the maximum value of p13, p34, p42, p21, for example, p13 in fig. 5, in which the 1-cylinder 11 cylinder pressure is abnormal, the 1-cylinder 11 cylinder pressure is considered abnormal;
b. if p13 is smaller than 0, the combustion excitation energy change rate of the 1 cylinder 11 is considered to be obviously smaller than that of the 3 cylinder 13, and the combustion excitation energy change rate is considered to be caused by that the cylinder pressure of one cylinder is reduced, the 1 cylinder 11 is insufficient in power supply, and the ECU control strategy can improve the cylinder pressure of the next cylinder, namely the 3 cylinder 13 through modification of the fuel injection parameter, so that the cylinder pressure of the 3 cylinder 13 is increased; it is considered that p13 of less than 0 is 1 cylinder 11, resulting in a smaller cylinder pressure;
c. if p13 is greater than 0, the combustion activation energy variation rate of 1 cylinder 11 is considered to be greater than that of 3 cylinder 13, because if the cylinder pressure of one cylinder increases, the 1 cylinder 11 is excessively powered, and the ECU control strategy reduces the cylinder pressure of the next cylinder, i.e., 3 cylinder 13, by modification of the injection parameter, and therefore, the cylinder pressure of 3 cylinder 13 decreases; therefore, it is considered that a cylinder pressure of one cylinder having p13 greater than 0 is large;
d. in fig. 6, when p21 is the maximum under the abnormal cylinder pressure condition of the 2-cylinder 12 and p21 is smaller than 0, the cylinder pressure of the 2-cylinder 12 is considered to be reduced as compared with that under normal conditions.
It should be noted that, the processing signals by the algorithm include, but are not limited to, VMD algorithm, and may be related algorithms like EMD algorithm, EEMD algorithm, LMD algorithm, SVD algorithm, etc. similar to VMD algorithm, which all belong to the protection scope of the present application, and the following decomposition process of VMD algorithm is:
the variable mode decomposition is an adaptive signal processing method, and the original signal is decomposed into a plurality of eigenmode functions with limited bandwidth surrounding the center frequency by constructing a constraint variation model.
First construct a constrained variation model:
the goal of the VMD algorithm is to find the K eigenmode functions u under the constraint that the sum of the eigenmode functions is equal to the original signal x (t) k (t) minimizing the sum of the estimated bandwidths of each eigenmode function. Thus, the constraint variation model construction process of the VMD algorithm is as follows:
in the VMD algorithm, IMF is defined as an amplitude-frequency modulated signal:
the analytic signal of each IMF is obtained through Hilbert transformation, and a single-side spectrum is obtained:
mixing the estimated center frequencies in the form of exponential terms onto a single-sided spectrum, thereby modulating the spectrum of each IMF onto a corresponding baseband:
calculating the L of the demodulation signal gradient 2 The norm estimates the bandwidth of each IMF, and assuming that the original signal is decomposed into K IMF components, the corresponding constraint variation model is as follows:
wherein { u } k }＝{u 1 ，…u K Sum { omega } k }＝{ω 1 ，…ω K And the K IMF components obtained by VMD decomposition and the center frequency of each IMF are represented respectively.
Then solving a constraint variation model: in order to solve the optimal solution of the constrained variation model, the VMD introduces a quadratic penalty term factor alpha and a Lagrangian multiplier lambda (t) to transform the problem into an unconstrained variation problem; where α may guarantee the reconstruction accuracy of the signal and λ (t) may guarantee the strict execution of the constraint. Based on which an augmented lagrangian equation can be derived:
by this process, the minimum problem is converted into solving the Lagrangian saddle point problem, which can be updated continuously by the commutative number multiplication (Alternate Direction Method of Multipliers, ADMM)λ n+1 And stopping iteration until the given precision or the given iteration times are reached, and finally obtaining the optimal solution of the unconstrained problem.
From the above deductions, the calculation flow of the VMD algorithm can be expressed as follows:
initialization ofλ 1 And n=1;
according to the formulaUpdating u k ；
According to the formulaUpdating omega k ；
k=k+1, repeating steps b) and c) until k=k;
according to the formulaUpdating lambda;
given the discrimination precision epsilon < 0 and the maximum iteration number N, if the stopping condition is satisfiedOr n=n, stopping iteration, and outputting the result to obtain K IMFs; otherwise, let n=n+1, repeat steps b), c), d), e).
After the calculation is completed, K IMF components are obtained.
The number of decomposition layers adopted in the embodiment of the application is 6.
The vibration signal is subjected to VMD decomposition to obtain K IMF components, self-power spectral density analysis is carried out on each IMF component to obtain spectral information of each IMF component, and IMFs with the center frequency being the ignition frequency are selected from the spectral information.
The engine 10 combustion non-uniformity detection system and the detection method provided by the embodiment of the application have the following advantages:
1) The cylinder pressure non-uniformity or the misfire fault diagnosis is completed through the signals detected by the vibration sensor 20 and the pipe clamp sensor 30, and has advantages of low cost, high efficiency, and high accuracy compared with the existing diagnosis method. The method solves the problems of high cost, poor reliability (the sensor is easy to fail) and the like of the invasive detection means based on the cylinder pressure signal, and solves the problems of high cost, low efficiency and poor precision of the existing detection means based on the vibration signal;
2) The combustion excitation energy of each cylinder is obtained through VMD decomposition and analysis, and the non-uniformity diagnosis is carried out through the relative change rate of the combustion excitation energy of each cylinder, so that the problem that the method based on the rotation speed signal can only be used for the fire diagnosis of the engine 10 and can not be applied to the monitoring of the non-uniformity fault of combustion is solved.
In addition, the foregoing embodiments merely illustrate the technical features related to the improvement points of the present application, and do not represent that the fuel sample monitoring system and method of the present application does not have other technical features, and the other technical features will not be described in detail herein.
Those skilled in the art will appreciate that all or part of the steps in implementing the methods of the embodiments described above may be implemented by a program stored in a memory, including instructions for causing a (e.g., single-chip, etc.) or control device (e.g., processor) to perform all or part of the steps of the methods of the embodiments of the application. And the aforementioned memory includes: a U-disk, a removable hard disk, a Read-only memory (ROM), a random access memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
The present application is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present application are intended to be included in the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (6)
1. An engine combustion non-uniformity detection method, wherein the engine combustion non-uniformity detection method is implemented according to an engine combustion non-uniformity detection system, the engine combustion non-uniformity detection system comprising:
the vibration sensor is arranged on a cylinder block of the engine and is used for detecting a vibration signal of the cylinder block;
the pipe clamp sensor is arranged on a high-pressure oil pipe of the engine and used for detecting a pulse signal of the high-pressure oil pipe, and the pipe clamp sensor detects a firing phase of the engine through the high-pressure oil pipe of the engine;
the data acquisition card is electrically connected with the vibration sensor and the pipe clamp sensor respectively;
the controller is provided with a computer readable storage medium electrically connected with the data acquisition card and judges whether the engine burns unevenly or not according to the vibration signal and the high-pressure oil pipe pulse signal acquired by the data acquisition card;
the vibration sensor is arranged at the upper edge of the cylinder block and is positioned at the middle position among a plurality of cylinder blocks of the engine, and the vibration sensor is used for detecting vibration signals of the cylinder blocks at the same time;
the method for detecting the engine combustion non-uniformity comprises the following steps:
acquiring a vibration signal X1 of a cylinder body under a working condition to be detected and a pulse signal X2 of a high-pressure oil pipe;
acquiring a plurality of vibration signals X1 and generating signals X3 in a plurality of stroke cycles of the cylinder block, and acquiring a plurality of high-pressure oil pipe pulse signals X2 and generating signals X4;
correcting the oil injection advance angle of the cylinder block according to the signal X4, and then acquiring the top dead center position a of the cylinder block;
processing a signal X3 according to a VMD algorithm to obtain a signal X5, and acquiring combustion excitation energy h of the cylinder block corresponding to the top dead center position a according to the signal X5;
analyzing a plurality of combustion excitation energies h of a plurality of cylinder blocks of an engine, and judging whether the cylinder blocks of the engine are unevenly combusted according to the combustion excitation energies h;
the determining whether the plurality of cylinder blocks of the engine burn unevenly according to the plurality of combustion excitation energies h specifically includes:
comparing two of the combustion excitation energies h of the adjacent two cylinder blocks;
according to the fact that the difference value of the two combustion excitation energies h is larger than a preset difference value, judging that the combustion of the two adjacent cylinder blocks of the engine is uneven;
and if the difference value of the two combustion excitation energies h is larger than a preset difference value, judging that the adjacent two cylinder blocks of the engine are unevenly combusted, wherein the method further comprises the following steps:
according to the fact that the adjacent two cylinder blocks are unevenly combusted, and the combustion excitation energy h of the front cylinder block is larger than the combustion excitation energy h of the rear cylinder block, the cylinder pressure of the front cylinder block is judged to be increased, and the cylinder pressure of the rear cylinder block is judged to be reduced;
and according to the uneven combustion of the two adjacent cylinder blocks and the combustion excitation energy h of the front cylinder block is smaller than the combustion excitation energy h of the rear cylinder block, determining that the cylinder pressure of the front cylinder block is reduced and the cylinder pressure of the rear cylinder block is increased.
2. The method for detecting engine combustion non-uniformity according to claim 1, wherein said processing signal X3 according to VMD algorithm to obtain signal X5, and obtaining combustion excitation energy h of said cylinder block corresponding to said top dead center position a according to said signal X5 comprises:
acquiring mechanical excitation energy a of the cylinder block under an unburned state of the engine under a test working condition;
acquiring the vibration signal X3 of the cylinder block of the engine under the working condition to be detected, and calculating excitation energy A of the cylinder block according to the vibration signal X3;
and calculating the excitation energy A minus the mechanical excitation energy a to obtain the combustion excitation energy h of the cylinder block corresponding to the top dead center position a under the working condition to be detected.
3. The method for detecting engine combustion non-uniformity according to claim 2, wherein said obtaining mechanical excitation energy a of said cylinder block in an unburned state of said engine under test conditions specifically comprises:
controlling the engine to stably run in a reverse towing working condition in a test state;
recording ignition phase information under different rotating speeds and different air inflow and vibration signals of the cylinder body;
and calculating the mechanical excitation energy a of the cylinder body corresponding to the top dead center position a under the test working condition according to the ignition phase information and the vibration signal of the cylinder body.
4. The method for detecting engine combustion non-uniformity according to claim 3, wherein said recording ignition phase information at different rotational speeds, different intake air amounts, and vibration signals of said cylinder block specifically comprises:
and controlling the air inflow of the engine by adjusting the opening degree of an air inlet throttle valve, and recording the ignition phase and the vibration signal of the cylinder body under different rotating speeds and different air inlet flow rates.
5. The method for detecting engine combustion non-uniformity according to claim 3, wherein said processing signal X3 according to VMD algorithm to obtain signal X5, and obtaining combustion excitation energy h of said cylinder block corresponding to said top dead center position a according to said signal X5 further comprises:
decomposing the vibration signal X3 according to the VMD algorithm, and obtaining time domain signals ui separated by each IMF mode after VMD decomposition;
confirming the ignition phase information according to the signals X4 generated by the high-pressure oil pipe pulse signals X2;
the combustion excitation energy h is generated from the respective IMF modal components and the ignition phase information.
6. The method for detecting engine combustion non-uniformity according to claim 5, wherein said decomposing said vibration signal X3 according to said VMD algorithm to obtain time domain signals ui separated from each IMF mode after VMD decomposition further comprises:
calculating the self-power spectrum of each IMF modal component, and acquiring the center frequency Fi of each IMF modal component;
inquiring whether each center frequency Fi contains the engine ignition frequency, and readjusting VMD algorithm parameters if the center frequency Fi does not contain the engine ignition frequency until each IMF modal component containing the engine ignition frequency is obtained.
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