CN110530647B - Internal combustion engine health monitoring method based on acoustic emission technology and crankshaft instantaneous speed - Google Patents
Internal combustion engine health monitoring method based on acoustic emission technology and crankshaft instantaneous speed Download PDFInfo
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Abstract
本发明公开了一种基于声发射技术和曲轴瞬时转速的内燃机健康监测方法，包括以下步骤，步骤1、通过转速传感器采集内燃机飞轮的转速信息；步骤2、通过所述内燃机飞轮的转速信息计算内燃机中各缸的健康指数，判断内燃机中各缸工作是否正常；步骤3、若内燃机中各缸工作正常，返回步骤1；若内燃机中某个缸工作异常，进入步骤4；步骤4、通过所述工作异常的缸上设置的声发射传感器采集所述工作异常的缸的声发射信号；步骤5、根据所述声发射信号确定所述工作异常的缸的故障发生位置和故障类型。该方法可以精确地获得内燃机的出现故障的零部件和故障类型，以便于对其进行维护和维修。
The invention discloses a method for monitoring the health of an internal combustion engine based on acoustic emission technology and the instantaneous speed of a crankshaft. The health index of each cylinder in the internal combustion engine is used to determine whether each cylinder in the internal combustion engine works normally; Step 3, if each cylinder in the internal combustion engine works normally, return to step 1; if a certain cylinder in the internal combustion engine works abnormally, go to step 4; The acoustic emission sensor provided on the abnormally working cylinder collects the acoustic emission signal of the abnormally working cylinder; Step 5: Determine the fault location and fault type of the abnormally working cylinder according to the acoustic emission signal. The method can accurately obtain the faulty parts and fault types of the internal combustion engine, so as to facilitate its maintenance and repair.
Description
Technical Field
The invention relates to the technical field of internal combustion engine monitoring, in particular to an internal combustion engine health monitoring method based on an acoustic emission technology and the instantaneous rotating speed of a crankshaft.
Background
The combustion of the internal combustion engine and the movement of the piston assembly are complex dynamic processes and determine the performance, emission and reliability of the internal combustion engine, so that online state monitoring of the internal combustion engine is important for ensuring good combustion of the internal combustion engine, prolonging the reliability and service life of equipment, saving fuel consumption and reducing emission of pollutants.
The traditional combustion monitoring method is cylinder pressure monitoring. However, the cylinder pressure sensor has high cost, cannot work in a severe environment with high temperature and high pressure for a long time, and has a limited service life. The method for extracting characteristic parameters or reconstructing the pressure in the cylinder by using the vibration sensor arranged on the cylinder head to measure the vibration signal has the problems of low signal-to-noise ratio, more interference and low diagnosis precision.
The traditional method for monitoring the piston assembly is to check a scavenging port after the machine is stopped or measure related parameters of a cylinder sleeve and a piston ring and the like so as to judge the working state and the abrasion loss of the cylinder sleeve and the piston ring. The method for monitoring the wear condition of the piston ring in the running state mainly comprises a cylinder pressure monitoring method, an oil monitoring method, a magnetic sensing monitoring method and the like, and a lubricating oil film measuring technology based on a capacitance method, a laser induced fluorescence method, an optical fiber method and an ultrasonic imaging method. The detection methods have the characteristics, but some methods cannot reflect the lubricating state between the cylinder sleeve and the piston ring on line and in real time, and some methods can only measure the local information of the piston ring, so that the method has more limitations in implementation and is difficult to comprehensively, accurately and timely reflect the working state and early failure between the cylinder sleeve and the piston ring.
Disclosure of Invention
The invention provides an internal combustion engine health monitoring method based on an acoustic emission technology and the instantaneous rotating speed of a crankshaft, aiming at the problems, and the fault point of the internal combustion engine can be quickly and accurately obtained.
The technical means adopted by the invention are as follows:
a health monitoring method of an internal combustion engine based on an acoustic emission technology and the instantaneous rotating speed of a crankshaft comprises the following steps,
and 5, determining the fault occurrence position and the fault type of the cylinder with the abnormal work according to the acoustic emission signal.
Further, the health index of the cylinder in the step 2 is calculated by adopting the following formula,
wherein HiIs the health index of the i-th cylinder, va1For the corresponding instantaneous maximum value of the speed of rotation, v, after combustion in the cylindera2For the corresponding instantaneous maximum value of speed before combustion, v, of the cylinderbIs the minimum value of the instantaneous speed of the cylinder at the top dead center when HiA positive or zero value indicates that the cylinder is operating normally, when HiWhen the value is negative, the cylinder is indicated to work abnormally.
Further, the health index of the cylinder in the step 2 is calculated by adopting the following formula,
wherein HiIs the health index of the i-th cylinder, AaIs the sum of the corresponding positive instantaneous rotational accelerations after combustion in the cylinder, AbIs the absolute value of the sum of the corresponding negative instantaneous rotational accelerations before combustion in that cylinder;
when H is presentiA positive or zero value indicates that the cylinder is operating normally, when HiWhen the value is negative, the cylinder is indicated to work abnormally.
Further, said step 5 of determining a fault occurrence location and a fault type of said malfunctioning cylinder based on the acoustic emission signals comprises the steps of,
and step 51, comparing the relation curve of the characteristic value of the acoustic emission signal with the flywheel corner in abnormal work with the relation curve of the characteristic value of the acoustic emission signal of the cylinder in normal work with the flywheel corner to obtain the flywheel corner corresponding to the abnormal position of the characteristic value of the acoustic emission signal, determining the history of different events in the work cycle process of the cylinder corresponding to the abnormal position of the characteristic value of the acoustic emission signal according to the flywheel corner, and further obtaining the parts with faults and fault information.
Further, the characteristic values include frequency, energy and amplitude.
Further, the history of different events during the cylinder's duty cycle includes changes in-cylinder pressure, oil injection, combustion, friction between the piston assembly and the cylinder liner, and exhaust valve opening and closing.
Compared with the prior art, the internal combustion engine health monitoring method based on the acoustic emission technology and the crankshaft instantaneous rotating speed has the following beneficial effects: the method can accurately judge whether each cylinder in the internal combustion engine works normally, and can quickly judge the position and the part of the fault when a certain cylinder has the fault.
Drawings
FIG. 1 is a flow chart of a disclosed method for monitoring the health of an internal combustion engine based on acoustic emission technology and crankshaft instantaneous rotational speed;
FIG. 2 is a flow chart illustrating the determination of the fault location and fault type of the malfunctioning cylinder based on the acoustic emission signals according to the present disclosure;
FIG. 3 is a block diagram of a system for implementing the disclosed method;
FIG. 4 is a graph of raw signals of a flywheel collected by a speed sensor;
FIG. 5 is a graph of the relationship between the crankshaft instantaneous rotational speed and the crankshaft instantaneous acceleration (lateral view) calculated from the raw signals in FIG. 4 and the crankshaft rotational angle;
FIG. 6 is a graph of the instantaneous rotational speed and the instantaneous acceleration (circle graph) of the crankshaft calculated from the raw signals in FIG. 4 versus the rotational angle of the crankshaft;
FIG. 7 is a graph of the calculated individual cylinder health index profiles from FIG. 5;
FIG. 8 is a graph of acoustic emission raw signals collected over a duty cycle on a cylinder head surface in normal operation;
FIG. 9 is a frequency domain plot of the acoustic emission raw signal of FIG. 8 after Fourier transform (FFT);
FIG. 10 is a time-frequency distribution graph of acoustic emission raw signals subjected to short-time Fourier transform (STFT);
FIG. 11 is a graph of the time-frequency distribution after taking the logarithm of the signal of FIG. 10;
FIG. 12 is a graph of total energy obtained by summing the energy of all frequencies of the signal of FIG. 8;
FIG. 13 is a circumferential view of the total energy map of FIG. 12;
FIG. 14 is an enlarged time-frequency distribution graph of signals during fuel injection and combustion in the cylinder of FIG. 11;
FIG. 15 is a graph of log-scaled time-frequency distribution of signals during fuel injection and combustion;
FIG. 16 is a signal collected with an acoustic emission sensor positioned near an exhaust valve;
FIG. 17 is a time-frequency distribution graph after the logarithm of the signal in FIG. 16 is taken;
FIG. 18 is a circumferential plot of the root mean square value (RMS) of an acoustic emission signal collected when an acoustic emission sensor is disposed proximate an exhaust valve.
Detailed Description
Referring to fig. 1 and 2, the method for monitoring the health of an internal combustion engine based on acoustic emission technology and the instantaneous rotational speed of a crankshaft, disclosed by the invention, comprises the following steps,
Specifically, as shown in fig. 3, the system used in the present invention includes a rotation speed sensor, an acoustic emission sensor, an amplifier, a data acquisition card and a computer, wherein the rotation speed sensor is connected with the data acquisition card through a signal line, and the rotation speed sensor may be a conventional magnetoelectric or photoelectric sensor for measuring the rotation speed and rotation angle signals of the flywheel.
The acoustic emission sensor is connected with the amplifier through a signal line, the amplifier is connected with the data acquisition card, and the acoustic emission sensor can be placed on the outer surface of the cylinder head or the cylinder body and used for measuring acoustic emission signals related to the processes of oil injection, combustion, air intake and exhaust and motion of the piston assembly in the combustion chamber.
The amplifier is used for amplifying the acoustic emission signal.
The data acquisition card can realize the synchronous acquisition of multi-channel data and transmit signals acquired by the rotating speed sensor and the acoustic emission sensor to the computer.
The computer is used for storing, analyzing and displaying the collected data and can be a desktop computer or a notebook computer.
The signal line adopts the shielded wire.
The rotation speed sensor collects signals of the flywheel, the signals are input to a computer for digital filtering, and then the instantaneous rotation speed and the instantaneous rotation acceleration of the flywheel (crankshaft) are calculated, and further the health index of each cylinder is calculated.
The method for calculating the crank angle comprises the following steps: the number of the teeth of the flywheel is N, and the rotation of one circle is 360 degrees, so that the corresponding angle of each tooth is 360/N; the angle of each tooth can be located after finding the zero degree angle. The angle between two adjacent teeth is obtained by a linear interpolation method.
The instantaneous rotational speed is the speed of the flywheel (crankshaft) rotating through a certain minute rotational angle, and can be calculated according to the time of each tooth passing through the sensor (or the time difference of two adjacent teeth passing through the sensor). The time difference is calculated by adopting a zero point method. The zero point is the intersection point of the voltage signal curve and the zero line (the voltage changes from a positive value to a negative value and then changes to a positive zero point). And calculating the instantaneous rotating speed of the flywheel according to the difference between two adjacent positive (or negative) zero points.
The zero angle can be positioned according to the acoustic emission signal, because the acoustic emission signal changes suddenly when oil is injected and combusted in the cylinder, the variation (namely the first derivative of the signal) is larger than the variation of the acoustic emission signal corresponding to other angles, and the position, near the angle corresponding to the maximum first derivative of the signal, at which the instantaneous rotating speed is the lowest is the top dead center (zero angle). The zero-degree angle can also be positioned by setting a characteristic point on the flywheel, namely, finding a tooth corresponding to the rotating speed sensor when the cylinder is positioned at the top dead center on the flywheel, and setting a mark (characteristic point) on the tooth, wherein the corresponding angle is the zero-degree angle when the tooth rotates to the position of the rotating speed sensor every time.
The instantaneous rotational acceleration is the first derivative of the instantaneous rotational speed.
The relation curve of the flywheel rotation angle and the crankshaft instantaneous rotation speed (instantaneous acceleration) can be obtained by calculating the signals acquired by the speed sensor according to the method.
The health index reflects the work-doing capacity of each cylinder of the internal combustion engine and can be characterized by the instantaneous rotational speed of the crankshaft.
The health index may be calculated using the following formula,
wherein HiIs the health index of the i-th cylinder, va1For the corresponding instantaneous maximum value of the speed of rotation, v, after combustion in the cylindera2For the corresponding instantaneous maximum value of speed before combustion, v, of the cylinderbThe numerator in the above formula represents the combustion work-doing capacity of the cylinder for the minimum value of the instantaneous rotating speed of the cylinder at the top dead center, the denominator represents the work consumed by the resistance moment before the combustion of the cylinder, the numerator and the denominator are respectively squared to increase the sensitivity of the health index, and the subtraction of 1 aims to ensure that the health index is negative when the internal combustion engine fails, when H is the faultiA positive or zero value indicates that the cylinder is operating normally, when HiWhen the value is negative, the cylinder is indicated to work abnormally.
The health index may also be calculated by the following method,
wherein HiIs the health index of the i-th cylinder, AaIs the sum of the corresponding positive instantaneous rotational accelerations after combustion in the cylinder, AbIs the absolute value of the sum of the corresponding negative instantaneous rotational accelerations before combustion in that cylinder;
when H is presentiA positive or zero value indicates that the cylinder is operating normally, when HiWhen the value is negative, the abnormal operation of the cylinder is indicated
The physical significance of the health index represented by the formulas (1) and (2) is the ratio of the work capacity (i.e., power torque) and the resistance torque of each cylinder of the internal combustion engine, and then the health index is zeroed. When the internal combustion engine works normally, the health index of each cylinder is close to zero. When the health index is negative, the total resistance distance of the internal combustion engine in the angle range corresponding to the oil injection work of the cylinder is larger than the power torque, and the acting function is poor. The larger the negative absolute value, the worse the working capacity of the cylinder. The reasons for poor function include poor oil injection and combustion, faults of an air inlet system and an air exhaust system, large motion resistance of a piston, large resistance torque of a shafting and the like, and the specific reasons need to be analyzed and judged by combining instantaneous rotating speed, instantaneous acceleration and subsequent acoustic emission signals.
If the health index of a certain cylinder is a positive value or zero, the cylinder can be judged to work normally; if the health index of a certain cylinder is a negative value, the cylinder can be judged to be abnormal in work. When the abnormal work of a certain cylinder is determined, the following work is carried out, the acoustic emission sensor is arranged on the cylinder with the abnormal work, and the acoustic emission signal of the cylinder with the abnormal work is collected through the acoustic emission sensor; and determining the fault occurrence position and the fault type of the cylinder with the abnormal work according to the acoustic emission signal.
Specifically, the acoustic emission sensor can be placed on the outer surface of a cylinder head or a cylinder body of a cylinder with abnormal work and used for measuring acoustic emission signals related to the processes of oil injection, combustion, air intake and exhaust and piston assembly movement in a combustion chamber, and inputting the acquired acoustic emission signals to a computer, the computer performs time domain analysis (including root mean square value (RMS) analysis), frequency domain analysis (FFT) and time-frequency domain analysis (STFT, CWT) on the acoustic emission signals, finds out time domain and frequency domain characteristics, further obtains the frequency distribution characteristics of the acoustic emission signals, the relation curves of energy, flywheel rotation angle and amplitude and flywheel rotation angle, compares the curves with the characteristic values (namely the crank angle degree or range corresponding to each event) stored in the computer when the cylinder normally works, and can obtain the degree of the flywheel rotation angle corresponding to the abnormal characteristic values (frequency, energy or amplitude) of the acoustic emission signals, and then the history of the event in the working cycle process of the corresponding cylinder at the moment can be determined through the degree of the flywheel rotation angle, and the faulted parts and fault information can be further obtained.
When the corresponding event when the characteristic value of the acoustic emission signal of the cylinder is abnormal is obtained, the possible fault type and the fault part of the cylinder can be further determined through the table 1.
TABLE 1 Fault types and faulty Components for different events
The method can quickly and accurately acquire the health state of the internal combustion engine and accurately acquire the fault type and the fault parts of the internal combustion engine.
Example 1
The following are the corresponding data obtained from experiments conducted on a 5S35ME-B9 (ignition sequence: 1,4,3,2,5, stroke 1550mm, rated power 4350KW, rated speed 167RPM) diesel engine using the method disclosed in the present invention. During testing, the third cylinder and the fifth cylinder of the diesel engine are set to be not ignited, and the rotating speed is 100 RPM.
Fig. 4 shows the raw signals collected by the flywheel speed sensor.
Fig. 5 and 6 are graphs showing the instantaneous rotational speed and the instantaneous acceleration of the crankshaft calculated from the raw signals of fig. 4, in which the curve indicated by the arrow 1 is the change in the instantaneous rotational speed of the crankshaft with the rotational angle, the curve indicated by the arrow 2 (which is the contour lines of the regions a and B) is the change in the instantaneous acceleration with the rotational angle of the crankshaft, the region a indicates that the instantaneous acceleration is a positive value, and the region B indicates that the instantaneous acceleration is a negative value. Wherein, FIG. 5 is a horizontal graph (the horizontal coordinate is 0-360 degrees), which can intuitively represent the change of the instantaneous rotating speed and the instantaneous acceleration of each cylinder; fig. 6 is a circumferential graph, which can intuitively represent the position of the instantaneous speed and the instantaneous acceleration change of each cylinder. The peaks of the 5 acceleration curves shown in the figure represent the combustion work processes of 1 cylinder, 4 cylinders, 3 cylinders, 2 cylinders and 5 cylinders respectively in a left-to-right sequence.
The location, magnitude and shape of the corresponding instantaneous acceleration for each cylinder in fig. 5 and 6 is indicative of the combustion condition of that cylinder.
The zero point at which the instantaneous acceleration changes from negative to positive in fig. 5 and 6 is the top dead center position of the cylinder. The portion where the maximum value is located (i.e., the crank angle) is the portion where the power torque borne by the crankshaft is the largest, and this position is correlated with the combustion condition in the cylinder. If an early or late injection condition occurs, the angle is correspondingly early or late and the peak is reduced.
The magnitude of the instantaneous acceleration can represent the working capacity of the cylinder. If the cylinder is sprayed with fuel less, not timed or atomized well, resulting in poor combustion, the instantaneous acceleration will be reduced.
The instantaneous acceleration profile of fig. 5 and 6 shows a small step (indicated by C) at about 30 degrees after top dead center. This is because the two-stroke diesel engine is lubricated by oil injection, and when the piston ring group passes through the oil injection hole, the lubrication condition is improved, the frictional resistance is reduced, and the instantaneous acceleration is maintained constant or reduced. If the oil-filled lubrication is poor or fails, the instantaneous acceleration at that point will continue to decrease, i.e., the step disappears.
If the friction force of the piston assembly increases somewhere in the process of moving, the instantaneous acceleration of the corresponding position of the piston assembly is also reduced.
Fig. 7 is a distribution diagram of the individual cylinder health index calculated from the formula (1) according to fig. 5 and 6, in which the bar graph indicated by the arrow 1 represents the health index, the bar graph indicated by the arrow 2 represents the work capacity (power torque), and the bar graph indicated by the arrow 3 represents the resistance torque, all of which are dimensionless quantities. As can be seen from the figure, the 3-cylinder health index is-0.47 and the 5-cylinder health index is-0.53, significantly lower than the other cylinders, consistent with the conditions set by the test (3-cylinder and 5-cylinder deactivation).
Diesel engines are equipped with speed regulators for regulating and controlling the amount of fuel injected by the diesel engine in order to control the speed (usually PID control). When 3 cylinders and 5 cylinders stop oil supply, corresponding instantaneous rotating speed is reduced, and the speed regulator automatically adjusts the oil injection quantity of other cylinders so as to maintain the constant rotating speed. It can be seen from fig. 7 that the health index of 1 and 4 cylinders is significantly increased as a result of the increase in the amount of fuel injected by these two cylinders.
The acoustic emission signal reflects changes in conditions within the combustion chamber. Time domain analysis, frequency domain analysis (FFT) and time-frequency domain analysis (STFT, CWT) are carried out on the acoustic emission signals, and time domain and frequency domain characteristics are found out, so that the change of the working process of the single-cylinder combustion chamber along with the crank shaft angle is analyzed, and the method comprises the following steps: (1) the motion process of the piston; (2) oil supply, oil injection and combustion processes; (3) and (4) air inlet and exhaust processes.
The acoustic emission signals measured at the external surface of the diesel engine include a number of events (acoustic emission sources) including changes in-cylinder pressure, oil injection, combustion, friction between the piston assembly and the cylinder liner, exhaust valve opening and closing, and interference signals from other cylinders or other acoustic emission sources, among others. Each acoustic emission source attenuates during propagation. The measured information may vary depending on the location where the acoustic emission sensor is mounted. Therefore, in actual installation, the acoustic emission sensor should be installed near the location of the acoustic emission source to be measured (of interest), for example, on the cylinder head surface, on (or near) the injector, on (or near) the exhaust valve (or attachment), on the upper portion of the cylinder liner, in the middle portion of the cylinder liner, or in the lower portion of the cylinder liner, to measure the different acoustic emission sources with emphasis, respectively. In the present embodiment, as shown in fig. 8, the acoustic emission raw signal of one working cycle is collected on the surface of the cylinder head No. 1, and the abscissa is time (crank angle) and the ordinate is signal amplitude.
Fig. 9 is a frequency domain diagram of an original signal after fourier transform (FFT), where the abscissa is frequency and the ordinate is amplitude characteristics corresponding to frequency values, and spectral characteristics of the signal can be extracted through FFT.
Fig. 10 and 11 show the results of short-time fourier transform. The figure shows information in three dimensions: the abscissa is time (flywheel/crank angle), the ordinate is frequency, different grays represent the energy of a certain frequency signal at a certain time (angle), wherein fig. 10 is a time-frequency distribution graph of an acoustic emission original signal after short-time fourier transform (STFT), and fig. 11 is a time-frequency distribution graph after logarithm extraction. The time domain characteristics and the frequency spectrum characteristics of the main events in the process of one working cycle of the diesel engine can be extracted through the graph shown in fig. 10 and fig. 11.
In fig. 11, arrow 1 indicates the injection and combustion process near top dead center, and the duration is approximately 5 degrees before top dead center to 14 degrees after top dead center.
In fig. 11, an arrow 3 indicates an injection/combustion signal of an adjacent cylinder (cylinder No. 2).
In order to more intuitively represent the development process of each event, the invention carries out dimension transformation on the graph 8, namely, the graph is changed from three dimensions to two dimensions. The transformation method is to add the energies of all frequencies at a certain time (angle) to obtain the total energy at the time (angle), i.e. the energy time domain diagram shown in fig. 12, and the crank angle corresponding to the extreme point is indicated in the diagram. Several distinct peaks appear in fig. 12, arrow 1 being the injection and combustion process near top dead center, arrow 2 being the injection combustion signal of the adjacent cylinder, arrow 3 being the signal generated when the piston ring set passes the scavenging holes, and arrow 4 being the signal generated when the piston ring set passes the oil holes. FIG. 13 is a circumferential graph of an energy curve to more intuitively illustrate the relevant events and corresponding crank angles.
The oil injection and combustion are key links in the working cycle of the diesel engine, and the quality of the oil injection and combustion determines the efficiency of the diesel engine, so that the monitoring of the oil injection and combustion process and the quality is very important. In order to obtain information about fuel injection and combustion as much as possible, the region 1 in fig. 11 is enlarged to obtain a time-frequency diagram of the region, as shown in fig. 14 and 15.
The time-frequency diagrams and energy curves in fig. 14 and 15 clearly show the following processes and the corresponding crank angles: the corresponding angle is the fuel injection advance angle at the time of starting fuel injection, 2 is the angle of starting combustion, 3 is the angle of ending fuel injection, 4 is the angle corresponding to the maximum pressure in the cylinder, and 5 is a signal generated when the piston ring group passes through the fuel injection hole.
In order to obtain information related to the exhaust valve action, an acoustic emission sensor may be placed in proximity to the exhaust valve during monitoring, which may reduce attenuation of the acoustic emission signal generated by the exhaust valve. The resulting acoustic emission raw signal is shown in fig. 16, and the short-time fourier transform result is shown in fig. 17.
In fig. 17, an arrow 1 indicates a signal generated when the exhaust valve is opened and a corresponding angle, and an arrow 2 indicates a signal generated when the exhaust valve is closed and a corresponding angle. When the exhaust valve is closed, the acoustic emission signal not only contains airflow scouring when the exhaust channel is reduced, but also has a signal generated by metal impact, and the acoustic emission signal of the metal impact is distributed in a low-frequency area. And when the exhaust valve is opened, the acoustic emission signals of the airflow scouring are distributed in a high-frequency area.
FIG. 18 is a plot of the Root Mean Square (RMS) circumference of an acoustic emission signal, which also shows the history and corresponding angles of different events during a single duty cycle.
Events corresponding to the occurrence of faults and faulty components in the internal combustion engine can be monitored by the above analysis means and according to table 1.
The results are displayed on the computer in a graphic mode, and are intuitive and easy to understand. The graph can be an abscissa graph (namely the abscissa is time or a crank angle) or a circumference graph (namely the change of parameters along with the change of the crank angle is displayed by a circle graph), and the zooming and the moving of the graph, the display of related numerical values and the storage of calculation results can be realized.
Meanwhile, the acoustic emission signals can be converted into an audio format to be played, fast playing, slow playing and volume adjustment can be achieved, and the running process of the auditory perception device is used.
And moreover, the interception, amplification, analysis and storage of signals can be realized, so that microscopic information of equipment, namely information of extremely tiny space (up to micron level) released by the equipment in a short time (up to microsecond level), can be acquired and analyzed in a visual (two-dimensional or three-dimensional graph or curve) or auditory (audio) mode, thereby analyzing the microscopic processes of oil injection, combustion, air intake and exhaust, piston assembly movement, lubrication and the like of the internal combustion engine, finding early information of faults and eliminating the faults in a bud state.
The method can:
(1) monitoring the running state and health condition of the internal combustion engine in real time and providing characteristic information of equipment;
(2) early abnormal phenomena and fault information of the internal combustion engine are found in time, abrasion of moving parts is reduced, accidental fault or shutdown time of equipment is reduced, operation safety and production efficiency are improved, and the service life of the equipment is prolonged;
(3) the equipment works in an optimal state, the fuel consumption is reduced, the repair and maintenance cost is reduced, the operation cost is reduced, and meanwhile, the emission of pollutants is also reduced.
And the method also has the following advantages:
(1) the method belongs to non-intrusive monitoring, and the sensor only needs to be attached to the outer surface of the internal combustion engine, does not need to be modified, and does not influence the working process of the internal combustion engine;
(2) the system can find early information of the fault in time, and eliminate the fault in a sprouting state through processing, so that the unplanned shutdown and major faults are reduced;
(3) a plurality of parameters are synchronously acquired, the method is suitable for online and real-time monitoring, and the pertinence of signals is strong;
(4) the system has high sampling rate and high signal-to-noise ratio of the measured signal, and can eliminate the interference of environmental noise so as to monitor weak fault information;
(5) the equipment is simple to install and use, and has low requirement on the environment;
(6) the system can be used for monitoring different stages (such as running-in period, normal operation period and fault period) of the internal combustion engine, and can also be used for monitoring and diagnosing equipment which is difficult to monitor by conventional means such as a stern shaft, a bearing, a gear, a supercharger and the like or equipment which requires relatively high precision.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (2)
1. A health monitoring method of an internal combustion engine based on an acoustic emission technology and the instantaneous rotating speed of a crankshaft is characterized in that: comprises the following steps of (a) carrying out,
step 1, acquiring the rotating speed information of a flywheel of an internal combustion engine through a rotating speed sensor;
step 2, calculating the health index of each cylinder in the internal combustion engine according to the rotating speed information of the flywheel of the internal combustion engine, and judging whether each cylinder in the internal combustion engine works normally or not;
the health index of the cylinder is calculated using formula (1) or formula (2),
wherein HiIs the health index of the i-th cylinder, va1For the corresponding instantaneous maximum value of the speed of rotation, v, after combustion in the cylindera2For the corresponding instantaneous maximum value of speed before combustion, v, of the cylinderbIs the minimum value of the instantaneous speed of the cylinder at the top dead center when HiA positive or zero value indicates that the cylinder is operating normally, when HiWhen the numerical value is a negative value, indicating that the cylinder works abnormally;
wherein HiIs the health index of the i-th cylinder, AaIs the sum of the corresponding positive instantaneous rotational accelerations after combustion in the cylinder, AbIs the absolute value of the sum of the corresponding negative instantaneous rotational accelerations before combustion in that cylinder;
when H is presentiA positive or zero value indicates that the cylinder is operating normally, when HiWhen the numerical value is a negative value, indicating that the cylinder works abnormally;
step 3, if each cylinder in the internal combustion engine works normally, returning to the step 1; if a certain cylinder in the internal combustion engine works abnormally, entering a step 4;
step 4, collecting acoustic emission signals of the cylinder with abnormal work through an acoustic emission sensor arranged on the cylinder with abnormal work;
step 5, determining the fault occurrence position and the fault type of the cylinder with abnormal work according to the acoustic emission signals, wherein the step 5 comprises the following steps,
step 50, collecting acoustic emission signals with abnormal work, and performing time domain analysis, frequency domain analysis and time-frequency domain analysis on the acoustic emission signals with abnormal work to find out time domain and frequency domain characteristics so as to obtain relationship curves of frequency distribution characteristics and energy of the acoustic emission signals with abnormal work, and relationship curves of amplitude and flywheel rotation angles;
step 51, comparing the relation curve of the frequency distribution characteristic, the energy, the flywheel corner and the amplitude of the acoustic emission signal with the flywheel corner obtained when the work is abnormal with the relation curve of the characteristic value of the acoustic emission signal of the cylinder and the flywheel corner obtained when the work is normal, obtaining the flywheel corner corresponding to the abnormal position of the characteristic value of the acoustic emission signal, determining the history of different events in the work cycle process of the cylinder corresponding to the abnormal position of the characteristic value of the acoustic emission signal according to the flywheel corner, and further obtaining the parts with faults and fault information.
2. An internal combustion engine health monitoring method based on acoustic emission technology and crankshaft instantaneous rotational speed according to claim 1, characterized in that: the history of different events in the working cycle process of the cylinder comprises the change of the pressure in the cylinder, oil injection, combustion, friction between a piston assembly and a cylinder sleeve, and the opening and closing of an exhaust valve.
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