CN104035434A - Air leakage monitoring system for diesel engine air valve - Google Patents

Abstract

The present invention is a diesel engine air valve leakage monitoring system, which is composed of a sensor, a cylinder pressure amplifier, a junction box, an industrial computer and a hand-held signal acquisition controller, and the sensor includes an acoustic emission sensor (1) mounted on the diesel engine , cylinder pressure sensor (2), top dead center sensor (4), the input and output terminals of the hand-held signal acquisition controller are respectively connected with the acoustic emission sensor and an input interface of the junction box through data lines; the cylinder pressure amplifier input and output The terminals are respectively connected with the cylinder pressure sensor and the other input interface of the junction box through the data line; the other input interface of the junction box is also connected with the top dead center sensor through the data line; the output interface of the junction box is connected with the built-in The data acquisition card of the industrial computer is connected; the hand-held signal acquisition controller communicates with the industrial computer through RS485. The invention can facilitate remote control signal collection and can accurately detect the air leakage degree of the air valve.

Description

Leakage Monitoring System of Gas Valve in Diesel Engine

technical field

The invention relates to a set of systems for monitoring air leakage faults of diesel engine valves. The invention belongs to the technical field of machinery, and further relates to a method for diagnosing air leakage of a diesel engine valve by using acoustic emission signal monitoring technology in mechanical signal testing and fault diagnosis.

Background technique

The exhaust valve is one of the most failure-prone parts of a diesel engine. The reasons for the failure of the diesel engine gas valve can be summarized into two aspects: (1) the working condition of the exhaust valve is bad; (2) improper maintenance. Once the exhaust valve of the diesel engine fails, the exhaust valve will leak, and the valve disc and stem will break if it is serious.

The power, economy and emission of a diesel engine are often closely related to whether the exhaust valve of the diesel engine works normally. Real-time monitoring of the exhaust valve of the diesel engine can reflect the working status of the exhaust valve of the diesel engine in real time, detect the fault of the exhaust valve in time, and repair the exhaust valve in time, so as to effectively avoid the occurrence of serious accidents of the diesel engine. At the same time, diesel engine monitoring and diagnosis technology is one of the three core technologies of diesel engine intelligence. Therefore, the research on the monitoring and diagnosis technology of exhaust valve working state has strong engineering application value.

At present, the fault diagnosis method of exhaust valve of diesel engine generally adopts vibration monitoring method and thermal parameter monitoring method. Vibration monitoring method and thermal parameter monitoring method have been widely used at home and abroad. However, the technology of using acoustic emission method to monitor the air leakage of diesel engine valve is rarely reported at home and abroad. The acoustic emission signal has the following characteristics: ①Acoustic emission is a strain wave emission, which is very sensitive to the impact of high-pressure gas, has a high signal-to-noise ratio, and is less affected by the installation position of the sensor; ②The frequency range of the acoustic emission wave is wide, from a few Hz to Several MHz, its amplitude ranges from microscopic dislocation movement to large-scale macroscopic fracture, the signal is rich in information, and is not easily disturbed by external factors such as structural vibration; ③Acoustic emission diagnosis method has good portability and can detect faults earlier sign. To sum up, the use of acoustic emission technology to monitor air valve leakage has high accuracy and practical value.

Contents of the invention

The technical problem to be solved by the present invention is to provide a diesel engine air valve leakage monitoring system, which can realize the portable collection of signals, and use EMD technology to process the acoustic emission signal of the diesel engine cylinder head, quickly diagnose whether the diesel engine is leaking, and judge its The degree of air leakage.

The present invention solves its technical problem and adopts the following technical solutions:

The system for monitoring air leakage faults of diesel engine valves provided by the present invention is composed of sensors, cylinder pressure amplifiers, junction boxes, industrial computers and hand-held signal acquisition controllers, wherein: the sensors include acoustic emission sensors mounted on diesel engines, The input and output ends of the cylinder pressure sensor, the top dead center sensor, and the hand-held signal acquisition controller are respectively connected with the acoustic emission sensor and an input interface of the junction box through data lines; the input and output ends of the cylinder pressure amplifier are respectively connected with the cylinder The other input interface of the junction box is connected with the pressure sensor and the other input interface of the junction box; the other input interface of the junction box is also connected with the top dead center sensor through the data line; the output interface of the junction box is connected with the data acquisition card embedded in the industrial computer through the data line ; The hand-held signal acquisition controller communicates with the industrial computer using RS485.

The acoustic emission sensor is packaged in a hand-held adsorption support, and the sensor leads are led out from the hollow handle of the support.

The handheld adsorption support is composed of a hollow handle, a top cover, a base, a powerful magnet, a spring and a sleeve, wherein: 5 pieces of strong magnets are respectively embedded in 5 counterbores at the lower part of the base; the sleeve is installed at the upper part of the base. In the counterbore, the acoustic emission sensor is installed in the sleeve; the spring is installed in the counterbore of the top cover, and the top cover and the base are connected by screws; the hollow handle is welded on the side of the base.

There are 5 powerful magnets, which are circumferentially inlaid in the lower counterbore of the base.

The cylinder pressure sensor is installed in the indicator cock of the diesel engine.

The top dead center sensor adopts the SZMB-5 type magnetoelectric sensor, which is installed at the camshaft position of the diesel engine.

The handheld signal acquisition controller is composed of a microprocessor and a voltage conversion circuit electrically connected thereto, a JPAG debugging circuit, a keyboard input circuit, a liquid crystal display circuit, a serial port communication circuit and an acoustic emission signal amplifying circuit.

The above-mentioned diesel engine air valve leakage fault monitoring system provided by the present invention is used for diagnosing whether the diesel engine has air leakage and judging the degree of air leakage.

When the present invention is applied in diagnosing whether the diesel engine is leaking or not and judging the degree of the leaking, it first collects the surface acoustic emission signal of the cylinder head, the cylinder pressure signal, and the top dead center signal, a total of three signals, wherein the acoustic emission signal is collected through a hand-held signal After the controller is amplified, it enters the junction box. The cylinder pressure signal enters the junction box after passing through the cylinder pressure amplifier. The user remotely controls the storage of the three-way signals through the handheld signal acquisition controller; for the saved signals, the industrial computer analyzes and processes them, and then diagnoses whether the diesel engine valve is leaking and the result of the leaking degree.

Compared with the prior art, the present invention has the following main advantages:

(1) The design of the handheld adsorption support greatly simplifies the installation of the acoustic emission sensor;

(2) The hand-held signal acquisition controller communicates with the upper computer using RS485, which can remotely control the signal acquisition; the controller integrates the acoustic emission signal amplification circuit, which has the function of conditioning and amplifying the acoustic emission signal, making the acquisition of the acoustic emission signal more convenient convenient;

(3) For the first time, the EMD technology is used to process the acoustic emission signal of the diesel engine cylinder head caused by the air valve leakage. The characteristic parameters extracted based on this technology can effectively identify the characteristics of the acoustic emission signal of the air valve leakage, and the accuracy is high.

(4) The upper computer of the monitoring system is easy to operate, and all parameters are automatically configured.

Description of drawings

Figure 1 is the experimental data of the characteristic parameters.

Fig. 2 is the experimental data of the characteristic parameter (EMD energy entropy).

Fig. 3 is a schematic diagram of the overall structure of the air valve leakage monitoring system.

Fig. 4 is a top view of the handheld adsorption support.

Fig. 5 is a bottom view of the handheld adsorption support.

Fig. 6 is a diagram of the internal structure of the hand-held adsorption support.

Fig. 7 is an outline diagram of the handheld signal acquisition controller.

Fig. 8 is a schematic diagram of the internal structure of the handheld signal acquisition controller.

Figure 9 is a schematic diagram of the internal modules of the upper computer software.

Figure 10 is a time-domain diagram of the acoustic emission, top dead center, and cylinder pressure signals within one cycle.

Figure 11 is the communication process between the handheld acquisition controller and the host computer.

Fig. 12 is a schematic diagram of intercepting signals corresponding to the combustion section.

Fig. 13 is a waveform diagram of IMF components and residual sequences.

Fig. 14 is a fault diagnosis MAP diagram.

In the figure: 1. Acoustic emission sensor; 2. Cylinder pressure sensor; 3. Handheld signal acquisition controller; 4. Top dead center sensor; 5. Diesel engine; 6. Hollow handle; 7. Fixing screw; 8. Top cover; 9. Base; 10. Powerful magnet; 11. Sensor lead wire; 12. Spring; 13. Sleeve; 14. Acoustic emission sensor; 15. Front cover; 16. Acoustic emission signal input terminal; 17. Upper cover; 18 . Acoustic emission signal output terminal; 19. Power supply and serial port terminal; 20 rear cover; 21. Lower cover; 22. Combustion section signal.

Detailed ways

The present invention will be further described below through the examples and accompanying drawings, but the protection scope of the present invention should not be limited thereto.

The diesel engine air valve leakage monitoring system provided by the present invention is a diesel engine air valve leakage monitoring system based on acoustic emission technology. Its structure is shown in Figure 3. It consists of sensors, hand-held signal acquisition controllers, cylinder pressure amplifiers, Composed of a junction box and an industrial computer, wherein: the sensor includes an acoustic emission sensor 1, a cylinder pressure sensor 2, and a top dead center sensor 4 installed on the diesel engine. The acoustic emission sensor 1 is connected to the input end of the hand-held signal acquisition controller 3 through the data line, and the output end of the hand-held signal acquisition controller 3 is connected to an input interface of the junction box through the data line; the cylinder pressure sensor 2 is connected to the input port of the junction box through the data line The input end of the cylinder pressure amplifier is connected, and the output end of the cylinder pressure amplifier is connected with another input interface of the junction box through a data line; the top dead center sensor 4 is connected with another input interface of the junction box through a data line; the output interface of the junction box is connected through a data line The line is connected with the data acquisition card embedded in the industrial computer. The hand-held signal acquisition controller 3 communicates with the industrial computer using RS485.

The acoustic emission sensor 1 is a PK31 acoustic emission sensor from American PAC Company, with a peak sensitivity of 106dB, an operating bandwidth of 10kHz-100kHz, an adaptable temperature range of -35°C-160°C, and an impact limit of 500g. The acoustic emission sensor is packaged in a hand-held adsorption support, and its lead wires are drawn out from the hollow handle 7 of the support.

The hand-held adsorption support is used to install the acoustic emission sensor, and the air valve of which cylinder is monitored will be adsorbed on the corresponding cylinder head of the cylinder. The structure of the handheld adsorption support is shown in Figures 4 to 6, which consists of a hollow handle 6, a top cover 8, a base 9, a powerful magnet 10, a spring 12 and a sleeve 13. Wherein: there are 5 powerful magnets 10 in total, which are inlaid in the lower part of the base 9 in a circular shape; the sleeve 13 is installed in the counterbore of the base 9, and the acoustic emission sensor 14 is installed in the sleeve 13; the spring 12 is installed in the bottom of the top cover 8 In the counterbore, the top cover 8 and the base 9 are connected by four fixing screws 7; the hollow handle 6 is welded on the side of the base 9, and the wire of the acoustic emission sensor 14 is drawn out from the hollow handle 6.

The cylinder pressure sensor 2 is a 7013C charge-type pressure sensor from KISTLER Company, with a range of 0 bar-250 bar, a sensitivity of -40 PC/bar, a resonant frequency of 70 kHz, and an applicable temperature range of -50 to 350 degrees Celsius. The cylinder pressure sensor 2 is installed in the power indicator cock of the diesel engine.

The cylinder pressure amplifier adopts the 5018A type cylinder pressure amplifier of KISTLER Company, its measuring range is 2pC-2200000pC, the output voltage is -10V-10V, and the applicable temperature range is 0°C-50°C.

The top dead center sensor 4 adopts a SZMB-5 type magnetoelectric sensor, which is installed at the position of the camshaft. Its minimum output amplitude is 300mV, and the installation tooth spacing is 2mm.

The junction box adopts the BNC-2090 type junction box of NI Company, and the junction box has 22 BNC input interfaces.

The data acquisition card adopts PCI6115 high-speed acquisition card of NI Company, and its maximum sampling rate reaches 2M.

The industrial computer adopts Advantech IPC-610MB-L industrial computer, which is equipped with Intel I5 processor, memory 4G, video memory 1G, hard disk 500G, equipped with 2 RS232 ports, 6 USB2.0 ports and 4 PCI port.

The appearance of the handheld signal acquisition controller 3 is shown in FIG. 7 . The controller communicates with the host computer through RS485, and can remotely control the signal storage of the host computer, and input parameters such as the cylinder number, load and speed of the diesel engine corresponding to the current test signal to the host computer. In addition, the controller has the function of conditioning and amplifying the acoustic emission signal. Figure 8 is a schematic diagram of the internal composition of the handheld signal acquisition controller, which uses STM32F103VC as the microprocessor, and the external 12V power supply supplies power to the microprocessor and other chips through the LM2575 and AS1117 voltage conversion chips; the JPAG debugging circuit and the keyboard circuit are connected to the microprocessor The corresponding I/O port of the processor is connected, the LCD1602 liquid crystal display module is connected with the corresponding I/O port of the microprocessor, and the serial port communication circuit is connected with the corresponding I/O port of the microprocessor through the SP3485 chip. The acoustic emission signal input terminal is connected to the signal output terminal after passing through the relay and the signal amplification circuit, and the corresponding I/O port of the microprocessor is connected to the relay to control the opening and closing of the relay.

The present invention uses a hand-held signal acquisition controller to remotely control the acquisition of all signals, and utilizes EMD technology to process the acquired surface acoustic emission signal of the cylinder head, and the signal is decomposed into six eigenmode components representing different physical meanings, hereinafter referred to as IMF components . Through a large number of test analysis, it is found that the EMD energy entropy of the acoustic emission signal of the diesel engine cylinder head and the energy of the first eigenmode component IMF1 correspond to the air leakage degree of the valve. This monitoring system will calculate the signal according to their changes. The special diagnosis parameters, and then diagnose the current working state of the diesel engine valve.

The gas valve leakage monitoring system of diesel engine provided by the present invention, its working process is as follows:

1. Install the sensor, connect the cable, and turn on the power;

2. Open the upper computer software of the monitoring system, the schematic diagram of each module of the upper computer software is shown in Figure 9, wherein the parameter automatic configuration module can automatically set the acquisition parameters and analysis parameters when the software starts; the communication module is used to communicate with the handheld signal acquisition control The acquisition module is used to drive the acquisition card to collect data; the database module is used to save and manage data files; the signal analysis module performs EMD analysis on the data, extracts characteristic parameters, and obtains diagnostic results; the report module can be used to view And print the diagnosis result report; the help module can give the operation prompt of the software.

3. The hand-held signal acquisition controller prompts the user to connect to the host computer. After pressing OK, the controller connects with the host computer, and at the same time conducts the acoustic emission signal input and output circuits inside the controller. After the connection is successful, the host computer starts to collect Signal.

4. The upper computer starts to collect (at this time, it only collects the signal and does not save the signal), and collects 3 signals at the same time, namely the cylinder head acoustic emission signal, cylinder pressure signal, and top dead center signal. After the acoustic emission signal is amplified by the hand-held signal acquisition controller, it is connected to the junction box from the signal output end of the controller. The cylinder pressure signal is amplified by the cylinder pressure amplifier and then connected to the junction box. The top dead center signal directly enters the junction box. The three signals enter the acquisition card embedded in the industrial computer at the same time for data analysis, storage and other operations. As shown in Figure 10, the signal will be displayed at the same time after being periodically intercepted by the host computer software, and the displayed data will be refreshed every 1 second.

5. See Figure 11, the user uses the handheld acquisition controller to send a save instruction to the host computer, and sends parameter information such as load, cylinder number, and speed to the host computer. After receiving the instruction, the upper computer will save the currently collected signal and signal parameter information within 5 seconds.

6. After the saving is completed, the host machine waits for the next saving command, and intercepts the burning section of the latest saved signal. Because when the gas valve leaks, it is mainly the signal of the combustion section (25CA before the combustion top dead center to 50CA after the combustion top dead center) is affected. Fig. 12 is a schematic diagram showing the signal interception of the combustion section in one cycle.

7. The software will perform EMD decomposition on the acoustic emission signal of the combustion section intercepted in each period, and can decompose to obtain 6 IMF components and 1 residual component R. As shown in Figure 13.

8. Calculate _the percentages P ₁ , P ₂ , P ₃ .

$<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}}$

$<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1,2</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>$

Among them, P _i is the percentage of the i-th IMF component to the total energy of the signal.

9. Average the calculated θ and ε values for 50 cycles, and take the average is the abscissa, As the vertical coordinate, the point Calibration is performed on the coordinate diagram. Then compare the calibration points with the fault diagnosis MAP shown in Figure 14 (the MAP is obtained from a large number of actual machine fault simulation tests). In Figure 14:

a＝-0.0128X ² +0.88X+23

b＝-0.0032X ² +0.224X+15

Wherein, X is the current load, for example, if the load is 75%, then X is equal to 75.

10. Save the measured signal and calculated characteristic parameters in the database, and display the valve diagnosis results on the software operation interface of the host computer.

11. Through the above analysis and processing, make a diagnosis decision.

To sum up, the system has completed the diagnosis of diesel engine valve faults, and the diagnosis system is highly intelligent.

Through experiments, the diesel engine air valve leakage monitoring system provided by the present invention has signal characteristic parameter test data in different valve states as shown in Figures 1 to 2, and the definition of characteristic parameters is as described above; Table 1 shows the percentage data of the energy of the six IMF components in the total energy.

Table 1 The percentage of the energy of the first 6 IMF components in the total energy of different valve states (%)

Claims (9)

1. the system of a diesel valve principal fault monitoring, it is characterized in that pressing amplifier, terminal box, industrial computer and hand-held signal acquisition controller to form by sensor, cylinder, wherein: described sensor comprises the calibrate AE sensor (1), cylinder pressure sensor (2), the TDCS TDC Sensor (4) that are contained on diesel engine, the input and output side of hand-held signal acquisition controller (3) is connected with an input interface of calibrate AE sensor (1), terminal box by data line respectively; Cylinder presses amplifier input and output side to be connected with another input interface of cylinder pressure sensor (2), terminal box by data line respectively; Another input interface of this terminal box is also connected with TDCS TDC Sensor (4) by data line; The output interface of terminal box is connected with the data collecting card that is embedded in industrial computer by data line; Hand-held signal acquisition controller (3) utilizes RS485 to communicate with industrial computer.

2. the system of diesel valve principal fault monitoring according to claim 1, is characterized in that described calibrate AE sensor (1) is encapsulated in hand-held absorption bearing, and sensor lead is drawn by the hollow handle (6) of this bearing.

3. the system of diesel valve principal fault monitoring according to claim 2, it is characterized in that described hand-held absorption bearing is made up of hollow handle (6), top cover (8), base (9), strong magnets (10), spring (12) and sleeve (13), wherein: strong magnets (10) is embedded in the counterbore of base (9) bottom; Sleeve (13) is arranged in the counterbore of base (9), and calibrate AE sensor (14) is arranged in sleeve (13); Spring (12) is arranged in the counterbore of top cover (8), and top cover (8) is connected by screw (7) with base (9); Hollow handle (6) is welded on the side of base (9).

4. the system of diesel valve principal fault according to claim 3 monitoring, is characterized in that described strong magnets (10) has 5, is in the bottom counterbore that circumferential is embedded in base (9).

5. the system of diesel valve principal fault monitoring according to claim 1, is characterized in that described cylinder pressure sensor (2) is arranged on showing in merit cock of diesel engine.

6. the system of diesel valve principal fault monitoring according to claim 1, is characterized in that described TDCS TDC Sensor (4) adopts SZMB-5 type magnetoelectric sensor, is installed on the camshaft location of diesel engine.

7. the system of diesel valve principal fault monitoring according to claim 1, it is characterized in that described hand-held signal acquisition controller (3), formed by voltage conversion circuit, JPAG debug circuit, keyboard input circuit, liquid crystal display circuit, serial communication circuit and the acoustic emission signal amplifying circuit of microprocessor and electrical connection with it.

8. the purposes of the system that in claim 1 to 7, described in arbitrary claim, diesel valve principal fault is monitored, is characterized in that whether leaking gas at Diagnosis of Diesel, judges the application in its gas leakage degree.

9. purposes according to claim 8, it is characterized in that first gathering cylinder lid surface acoustic emission signal, cylinder pressure signal, top dead centre signal Gong San road signal, wherein acoustic emission signal is amplified into terminal box through hand-held signal acquisition controller, cylinder pressure signal enters terminal box after cylinder is pressed amplifier, and top dead centre signal directly enters terminal box; Then three road signals are entered after capture card by terminal box, on industrial computer, show simultaneously, are now carried out the preservation of Long-distance Control three road signals by hand-held signal acquisition controller by user; For the signal of having preserved, industrial computer is analyzed and is processed it, so diagnose out diesel valve whether leak gas and its gas leakage degree result.