CN118961823A - An oil sensor and a full-flow online oil characteristic monitoring method - Google Patents
An oil sensor and a full-flow online oil characteristic monitoring method Download PDFInfo
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Abstract
本发明属于油液传感器技术领域，涉及一种油液传感器及一种全流量在线油液特性监测方法，油液传感器包括绝缘管、左环形静电感应电极、弧形电极、右环形静电感应电极；绝缘管水平放置，且平行于左右方向；弧形电极和左、右环形静电感应电极均依次间隔套在绝缘管上；监测方法为：将油液传感器安装于机械润滑系统循环回路的主油路上，控制机械润滑系统循环回路的油液全部从油液传感器的绝缘管中流过，同时给弧形电极施加初始激励电压后，对信号采集模块采集到的信号进行处理，即得油液特性。本发明可基于静电感应效应获得油液磨粒特性，并基于边缘电场效应获得油液温度的变化值，使油液磨粒特性监测更准确，同时实时测量油液的含水量。
The present invention belongs to the technical field of oil sensors, and relates to an oil sensor and a full-flow online oil characteristic monitoring method, wherein the oil sensor comprises an insulating tube, a left annular electrostatic induction electrode, an arc electrode, and a right annular electrostatic induction electrode; the insulating tube is placed horizontally and parallel to the left and right directions; the arc electrode and the left and right annular electrostatic induction electrodes are sequentially spaced on the insulating tube; the monitoring method is: the oil sensor is installed on the main oil circuit of the mechanical lubrication system circulation loop, and the oil in the mechanical lubrication system circulation loop is controlled to flow through the insulating tube of the oil sensor, and after applying an initial excitation voltage to the arc electrode, the signal collected by the signal acquisition module is processed to obtain the oil characteristic. The present invention can obtain the oil abrasive particle characteristics based on the electrostatic induction effect, and obtain the change value of the oil temperature based on the edge electric field effect, so that the oil abrasive particle characteristics monitoring is more accurate, and the water content of the oil is measured in real time.
Description
Technical Field
The invention belongs to the technical field of oil sensors, and relates to an oil sensor and a full-flow online oil characteristic monitoring method.
Background
The mechanical lubrication system is intended to lubricate and cool the relatively moving parts in the mechanical system, ensuring a stable operation of the system. However, abrasive particles generated by friction and abrasion may cause malfunction of the apparatus after a long period of operation. Therefore, the wear state of the mechanical equipment can be found in time by monitoring the abrasive particles in the lubricating oil loop on line in real time, and faults are prevented.
Component materials in current mechanical systems are increasingly diversified, and new nonmetallic materials such as ceramics are increasingly widely used. Unfortunately, conventional electromagnetic induction sensors have limitations in monitoring these nonmetallic materials, for example, the wind power generation online oil analysis device based on magnetic permeability disclosed in patent CN201837574U can monitor ferromagnetic abrasive particles, but cannot monitor nonmetallic materials such as ceramics. Moreover, existing oil sensors are also mostly only monitored for a specific feature in the oil, such as metal abrasive particles or water content. These prior art sensors have limited their range of application to some extent due to the single nature of the function.
In order to overcome these limitations, it is important to develop an oil sensor that can simultaneously monitor oil characteristics such as oil abrasive particle characteristics and water content.
Disclosure of Invention
The invention aims to solve the problems in the prior art and provides an oil liquid sensor and a full-flow online oil liquid characteristic monitoring method.
In order to achieve the above purpose, the invention adopts the following scheme:
An oil liquid sensor comprises an insulating tube, a left annular electrostatic induction electrode, an arc electrode, a right annular electrostatic induction electrode, a signal conditioning module and a signal acquisition module;
The insulating tube is horizontally arranged and parallel to the left-right direction;
the left annular electrostatic induction electrode, the arc electrode and the right annular electrostatic induction electrode are sleeved on the insulating tube and are sequentially arranged at intervals from left to right;
the left annular electrostatic induction electrode and the right annular electrostatic induction electrode are simultaneously connected with a signal conditioning module, and the signal conditioning module is used for conditioning signals on the left annular electrostatic induction electrode and the right annular electrostatic induction electrode;
the signal acquisition module is used for acquiring signals output by the signal conditioning module.
As a preferable technical scheme:
The oil sensor further comprises a metal shielding cover, a left sealing ring and a right sealing ring; the metal shielding cover is sleeved on the insulating tube and is in sealing connection with the insulating tube through the left sealing ring and the right sealing ring; the left annular electrostatic induction electrode, the arc electrode and the right annular electrostatic induction electrode are all positioned in the metal shielding cover, and the metal shielding cover plays roles of electromagnetic interference prevention and mechanical protection.
According to the oil liquid sensor, the length of the oil liquid sensor along the left-right direction is 56-70mm, the maximum outer diameter of the oil liquid sensor is 20-32mm, the outer diameter of the insulating tube is 8-20mm, the wall thickness of the insulating tube is 2mm, the wall thickness of the metal shielding cover is 4mm, the radian of the arc electrode is pi/2 rad, the outer diameters of the left annular electrostatic induction electrode, the arc electrode and the right annular electrostatic induction electrode are 12-24mm, the length of the left annular electrostatic induction electrode along the left-right direction is 6-24mm, and the distances between the arc electrode and the left annular electrostatic induction electrode and between the arc electrode and the right annular electrostatic induction electrode are 3-6mm.
According to the oil sensor, the insulating tube is made of PTFE, and the PTFE has the special properties of excellent electrical insulation, chemical stability and wide temperature and frequency range.
The oil sensor according to any one of the above claims, wherein the signal conditioning module is composed of a fringe capacitance detection circuit and a charge amplifier circuit; the signal acquisition module is composed of a data acquisition card or an integrated AD/DA conversion module.
According to the oil liquid sensor, the lengths of the left annular electrostatic induction electrode, the arc electrode and the right annular electrostatic induction electrode along the left-right direction are the same.
The invention also provides a full-flow online oil characteristic monitoring method adopting the oil sensor, which is characterized in that the oil sensor is arranged on a main oil path of a mechanical lubrication system circulation loop, oil in the mechanical lubrication system circulation loop is controlled to flow through an insulating pipe of the oil sensor, and an initial excitation voltage is applied to an arc electrode, and signals acquired by a signal acquisition module are processed to obtain oil characteristics;
The left annular electrostatic induction electrode or the right annular electrostatic induction electrode in the oil liquid sensor and abrasive particles jointly form an electrostatic induction sensor, the left annular electrostatic induction electrode or the right annular electrostatic induction electrode in the oil liquid sensor and the arc electrode jointly form a fringe electric field sensor, signals on the left annular electrostatic induction electrode are fringe capacitance signals a and electrostatic induction signals c, and signals on the right annular electrostatic induction electrode are fringe capacitance signals b and electrostatic induction signals d;
The signal conditioning module performs signal conversion and amplification of capacitance-voltage on the edge capacitance signal a and the edge capacitance signal b by using the edge capacitance detection circuit to obtain a voltage signal e, and performs signal conversion and amplification of charge-voltage on the electrostatic induction signal c and the electrostatic induction signal d by using the charge amplifier circuit to obtain a voltage signal f.
As a preferable technical scheme:
According to the full-flow online oil characteristic monitoring method, the oil characteristic comprises the abrasive particle characteristic and the change value of the oil temperature before and after the oil enters the insulating tube, and the calculation formula of the change value of the oil temperature before and after the oil enters the insulating tube is as follows:
wherein Δt represents the value of the change in oil temperature before and after oil enters the insulating tube in units of "C 21" represents the value of the fringe capacitance signal a in units of pf, C 22 represents the value of the fringe capacitance signal b in units of pf, L represents the value of the length of the left annular electrostatic induction electrode in units of mm in the left-right direction, θ represents the value of the radian of the arc electrode in units of rad, γ represents the edge proportionality coefficient (no unit, the value of which can be obtained by looking up the literature "Zhao Junming, wang Wenlian. Edge electric field sensor measures the thickness of the insulating layer of the metal substrate [ J ]). Sensor technology journal, 2018,31 (11): 1657-1661."), ε t0 represents the oil dielectric constant at the oil temperature before oil enters the insulating tube (no unit, the value of which is determined according to the specific experimental temperature and the specific oil type used, is the attribute value), and α ε represents the temperature coefficient of the dielectric constant (no unit, the value of which can be obtained by looking up the literature "Han Tingting. Southern industrial in the southern industrial university;
when the formula is calculated, only numerical values are substituted, and units are not substituted.
The accuracy of acquiring the abrasive particle characteristics is improved by acquiring the change value of the oil temperature;
the abrasive particle characteristics include an abrasive particle equivalent diameter value, abrasive particle material type, and the like; the method for obtaining the equivalent diameter value of the abrasive particles in the prior art comprises the following general steps: (a) Introducing oil with known abrasive particle equivalent diameters into the electrostatic induction sensor to obtain a voltage value of a voltage signal f, and repeating the steps to obtain the voltage values of the voltage signals f corresponding to different abrasive particle equivalent diameters; (b) Introducing oil with unknown equivalent abrasive particle diameter into the electrostatic induction sensor to obtain a voltage value of a voltage signal f, and comparing the voltage value with the voltage value of the voltage signal f obtained in the step (a), wherein the equivalent abrasive particle diameter corresponding to the voltage value of the voltage signal f which is the most similar to the voltage value of the voltage signal f is the equivalent abrasive particle diameter of the oil; the prior art method for obtaining the abrasive particle material type comprises the following general steps: (a) Introducing oil with known abrasive particle material types into the electrostatic induction sensor to obtain waveforms of voltage signals f, and repeating the steps to obtain waveforms of the voltage signals f corresponding to different abrasive particle material types; (b) And (c) introducing oil liquid with unknown abrasive particle material types into the electrostatic induction sensor to obtain waveforms of voltage signals f, comparing the waveforms with the waveforms of the voltage signals f obtained in the step (a), and obtaining the abrasive particle material type corresponding to the waveform of the voltage signal f which is the most similar to the waveform of the voltage signal f, namely the abrasive particle material type of the oil liquid.
However, the change of the oil temperature can have a certain influence on the monitoring precision of the electrostatic induction sensor: the working principle of the electrostatic induction sensor relates to charge distribution of the surface of an object, and temperature change can influence the charge distribution condition of the surface of the object, so that the sensitivity and the stability of the sensor are influenced; temperature variations can also affect the electrical characteristics of the object, such as conductivity and permittivity, which can affect the charge exchange between the electrostatic induction sensor and the object being measured, and thus the accuracy of the sensor monitoring.
After the method of the invention is adopted to obtain the variation value of the oil temperature, the specific corresponding relation of the oil temperature variation to the monitoring influence of the electrostatic induction sensor is obtained through experiments or searching literature data, and the influence signal is removed from the voltage signal f to obtain more real output voltage data, thereby being beneficial to further analysis and processing and accurately obtaining the abrasive particle characteristics.
The prior art discloses a plurality of temperature measuring methods, and most typically, various temperature sensors are used for directly measuring temperature, and the change value of the oil temperature is directly converted into voltage change for display analysis. However, the electrostatic induction sensor is small in size and is not suitable for adding more temperature sensors only for temperature measurement, and the problem that the change value of the oil temperature of the electrostatic induction sensor with small size is difficult to measure in the prior art is solved by coupling the electrostatic induction sensor with the fringe electric field sensor.
The full-flow online oil characteristic monitoring method comprises the following steps of: firstly, obtaining a change value A of a dielectric constant caused by moisture and abrasive particles flowing through an electrode before and after oil enters an insulating tube according to a voltage signal e, obtaining a change value B of the dielectric constant caused by the abrasive particles flowing through the electrode before and after the oil enters the insulating tube according to the voltage signal f, subtracting the change value B of the dielectric constant from the change value A of the dielectric constant to obtain a change value C of the dielectric constant caused by moisture before and after the oil enters the insulating tube, and finally obtaining the water content of the oil according to the change value C of the dielectric constant through searching data (documents Zhang Yong, sun Zhenyu, xue Chengxiong, and the like).
The current on-line monitoring method of the water content of the oil mainly comprises a microwave method, a ray method and a dielectric constant method.
The microwave method is a method for distinguishing moisture by applying electromagnetic waves in lubricating oil liquid, and because water belongs to a conductive medium, induced current can be generated in an electromagnetic wave environment, and the actual moisture content can be calculated in real time by a computer as long as the induced current under different moisture contents is measured;
The principle of the ray method is that the attenuation degree is different when gamma rays pass through lubricating oil and water, in theory, the gamma rays can produce attenuation of different degrees when passing through oil with different water contents, and the water content of the lubricating oil can be calculated by analyzing and calibrating the gamma rays received by the ray method;
The dielectric constant method applied to the capacitive sensor is the most widely used method for monitoring moisture on line, and is realized according to the principle that the change of the dielectric constant of a measured object causes the change of a capacitance value, namely, different water contents correspond to different dielectric constants, and different dielectric constants correspond to different capacitance values, so that the water content can be deduced according to the measured capacitance value.
The water content online monitoring method is a method applied by combining the condition of the composite sensor based on the water content detection principle of the existing capacitance sensor, and the change value of the dielectric constant of the medium obtained by the fringe field sensor is mainly caused by three factors: the moisture existing in the oil, the abrasive particles flowing through the electrode and the temperature change of the oil have been analyzed, the influence of the temperature change of the oil on the dielectric constant of the medium can be analyzed, only the factors of the abrasive particles and the moisture of the oil can be considered, the abrasive particles are monitored by using an electrostatic induction principle through an electrostatic induction sensor, the influence of the abrasive particles flowing through the electrode on the dielectric constant is eliminated, and the monitoring of the water content in the oil is realized.
The mechanism of the invention is as follows:
the oil sensor is equivalent to coupling an electrostatic induction sensor with a fringe field sensor;
As shown in fig. 3, the electrostatic induction sensor is composed of abrasive particles (exciting charges) flowing through the electrode and a receiving electrode plate (left annular electrostatic induction electrode and right annular electrostatic induction electrode), when the abrasive particles flow through the receiving electrode plate, charges in the receiving electrode plate are redistributed due to interaction between the charges, heterogeneous charges are attracted to one side close to the abrasive particles, and homogeneous charges are repelled to the other side far from the abrasive particles, so that certain induction charges (electrostatic induction signals) are generated on the surface of the receiving electrode plate;
as shown in fig. 2, the fringe field sensor is composed of an excitation electrode plate (arc electrode) and a receiving electrode plate (left annular electrostatic induction electrode and right annular electrostatic induction electrode) to which an initial excitation voltage is applied, and is analogous to the principle that a conventional capacitive sensor generates an electric field between upper and lower opposite electrode plates, the fringe field sensor generates an electrostatic field between the excitation electrode plate and the receiving electrode plate, the distribution of electric lines of force is radial, and meanwhile, analogous to the conventional capacitive sensor, the fringe field sensor generates a certain induction charge (fringe capacitance signal) on the surface of the receiving electrode plate;
the coupling means that the fringe electric field effect and the electrostatic induction effect are coupled together, the left annular electrostatic induction electrode and the right annular electrostatic induction electrode are used as components of the electrostatic induction sensor and the fringe electric field sensor, and signals output by the left annular electrostatic induction electrode and the right annular electrostatic induction electrode comprise fringe capacitance signals and electrostatic induction signals;
The coupling is that on the basis of utilizing the electrostatic induction sensor to obtain the abrasive particle characteristics, the fringe electric field sensor can be utilized to obtain the change value and the water content of the oil temperature at the same time, so that the synchronous acquisition of multidimensional data is realized, further, the influence of the oil temperature change on the monitoring of the abrasive particle characteristics by the electrostatic induction sensor is reduced or even eliminated, so that the accuracy of acquiring the abrasive particle characteristics is improved, the electrostatic induction sensor and the fringe electric field sensor are overlapped together in each single effect, the monitoring accuracy of the electrostatic induction sensor is optimized, and meanwhile, the two electrostatic induction sensors (an excitation charge and a left annular electrostatic induction electrode form one electrostatic induction sensor to a certain extent through the coupling of one fringe electric field sensor, and the excitation charge and a right annular electrostatic induction electrode form the other electrostatic induction sensor) are isolated, so that the influence of mutual interference is reduced.
The principle of acquiring the change value of the oil temperature by using the fringe field sensor is as follows:
When the upper and lower opposite-placed parallel polar plates of the traditional capacitor are placed on the same side, an electrostatic field is generated between the excitation polar plate and the receiving polar plate, so that the electric field at the edge is unevenly distributed, and the edge electric field effect of the capacitor is caused; the fringe electric field sensor is a composite sensor with three electrodes (a left annular electrostatic induction electrode, a right annular electrostatic induction electrode and an arc electrode), a certain fringe electric field effect exists between every two adjacent electrodes, as shown in figure 2, the distribution of electric lines of force is radial, an electric field is mainly concentrated between an excitation polar plate and a receiving polar plate, the fringe electric field effect is equivalent to that of a capacitor connected in parallel in the capacitor of the sensor, and a corresponding equivalent circuit is shown in figure 4;
Therefore, the fringe field sensor of the present invention is equivalent to a fringe field sensor composed of five capacitors (an arc electrode and a left ring-shaped electrostatic induction electrode form a fringe capacitor, an arc electrode and a right ring-shaped electrostatic induction electrode form a fringe capacitor, an arc electrode and a lubricating oil layer form a parallel plate capacitor, a left ring-shaped electrostatic induction electrode and a lubricating oil layer form a parallel plate capacitor, a right ring-shaped electrostatic induction electrode and a lubricating oil layer form a parallel plate capacitor), wherein C 21 and C 22 respectively represent the values of two fringe capacitance signals in pf, and C 11、C12、C13 respectively represent the values of three parallel plate capacitance signals in pf, and for C 21 and C 22, it can be represented by the following formulas:
Wherein epsilon 0 represents the vacuum dielectric constant (no unit), epsilon 1 and epsilon 2 represent the relative composite dielectric constant (no unit) corresponding to the fringe electric field, gamma represents the fringe proportionality coefficient (no unit), L represents the value of the length of the left annular electrostatic induction electrode in mm along the left-right direction, and theta represents the value of the radian of the arc electrode in rad (as shown in fig. 5);
The value of the capacitance signal measured by the fringe field sensor can reflect the medium distribution condition of the measured object at different temperatures to a certain extent. When the abrasive particles pass through the electrodes, the fringe electric fields between the electrodes are changed, namely C 21 and C 22 are changed, so that the relative composite dielectric constants epsilon 1 and epsilon 2 corresponding to the fringe electric fields are also changed, a certain relation exists between the dielectric constants of the medium and the oil temperature, and in the case of oil, epsilon t＝εt0(1+αε delta t), wherein epsilon t0 represents the oil dielectric constant (no unit) at the oil temperature before the oil enters the insulating tube, epsilon t represents the oil dielectric constant (no unit) at the oil temperature after the oil enters the insulating tube, delta t represents the change value of the oil temperature before and after the oil enters the insulating tube in units of DEG C, alpha ε represents the temperature coefficient (no unit) of the dielectric constant, the change of the relative composite dielectric constants epsilon 1 and epsilon 2 can be obtained through the change of C 21 and C 22, and the change of the relative composite dielectric constants epsilon 1 and epsilon 2 can be used for obtaining the change value delta t of the oil temperature, and the deduction process is as follows:
Due to Thus, it can be inferred that
Let ε t1 be the relative complex permittivity of the arc electrode and the fringe field formed by the left annular electrostatic induction electrode, ε t2 be the relative complex permittivity of the arc electrode and the fringe field formed by the right annular electrostatic induction electrode, ε t1＝ε0ε1,εt2＝ε0ε2 and ε t1＝εt0(1+αεΔt1),εt2＝εt0(1+αεΔt2) can be known by the definition of the permittivity, therefore:
The principle of acquiring the water content by using the fringe field sensor is as follows: the variation in dielectric constant of the medium obtained by the fringe field sensor is mainly caused by three factors: the influence of the temperature change of the oil on the dielectric constant of the medium is analyzed, only the factors of the oil particles and the moisture can be considered, and the electrostatic induction sensor can monitor the abrasive particles by applying the electrostatic induction principle, so that the influence of the abrasive particles flowing through the electrode on the dielectric constant is eliminated, and the monitoring of the water content in the oil is realized.
Advantageous effects
(1) According to the oil sensor, the arc-shaped electrodes with the radian theta are additionally arranged between the annular electrostatic induction electrodes, and the arc-shaped electrodes with the radian theta can be used for increasing the interval between the annular electrostatic induction electrodes, so that the aim of avoiding serious aliasing of output signals of the two electrodes is fulfilled.
(2) According to the full-flow online oil characteristic monitoring method, the oil abrasive particle characteristic can be obtained by applying the electrostatic induction effect, and the influence caused by monitoring the abrasive particle characteristic by the electrostatic induction sensor is reduced or even eliminated based on the temperature change obtained by the fringe electric field effect, so that the oil abrasive particle characteristic is monitored more accurately.
(3) According to the full-flow online oil characteristic monitoring method, the fringe electric field effect is applied, so that the dielectric constant change can be obtained, the oil temperature change can be obtained through the dielectric constant change, and the change part caused by the abrasive particles in the dielectric constant change can be stripped out based on the oil abrasive particle characteristic obtained by the electrostatic induction effect due to the fact that the dielectric constant change contains the interference change generated by a certain amount of moisture as a medium, so that the water content monitoring is realized.
(4) According to the invention, fringe electric field effect is firstly applied to the arc electrode from the classical plane electrode, and meanwhile, the electrostatic induction sensor and the fringe electric field sensor are coupled, so that on the basis of obtaining the abrasive particle characteristics, the change value of the oil temperature and the water content of the oil are obtained, the synchronous acquisition of multidimensional data is realized, and both metal and nonmetal materials can be used.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a full flow on-line oil sensor based on fringe field-electrostatic inductive coupling according to the present invention;
FIG. 2 is a schematic diagram of a fringe field sensor formed in the present invention;
FIG. 3 is a schematic diagram of an electrostatic induction sensor formed in the present invention;
FIG. 4 is an equivalent circuit diagram of the fringe capacitance effect of the present invention;
FIG. 5 is a schematic diagram of a cross-sectional structure of an oil sensor along the radial direction of an arc electrode;
FIG. 6 is a schematic diagram of a fringe capacitance sensing circuit of the present invention;
FIG. 7 is a circuit diagram of a charge amplifier of the present invention;
FIG. 8 is a flow chart of a signal acquisition module of the present invention;
FIG. 9 is a schematic diagram of a front panel of a signal acquisition module according to the present invention;
FIG. 10 is a graph showing the relationship between the capacitance Cap and the simulated oil temperature T measured in example 2 of the present invention;
FIG. 11 is a graph showing the comparison of the oil temperature measured by the temperature sensor according to the present invention with the oil temperature measured in example 2;
FIG. 12 is an enlarged view of a portion of the vicinity of the segment of data in FIG. 11 where t is 85-130 s;
The device comprises a positive charge abrasive particle flowing through oil, a 2-sealing ring, a 3-left annular electrostatic induction electrode, a 4-arc electrode, a 5-right annular electrostatic induction electrode, a 6-insulating tube, a 7-metal shielding cover, an 8-sealing ring, a 9-signal conditioning module, a 10-signal acquisition module, an 11-electrical interface and a 12-metal shielding cover.
Detailed Description
The application is further described below in conjunction with the detailed description. It is to be understood that these examples are illustrative of the present application and are not intended to limit the scope of the present application. Furthermore, it should be understood that various changes and modifications can be made by one skilled in the art after reading the teachings of the present application, and such equivalents are intended to fall within the scope of the application as defined in the appended claims.
Example 1
An oil sensor is shown in fig. 1, and comprises an insulating tube 6, a left annular electrostatic induction electrode 3, an arc electrode 4, a right annular electrostatic induction electrode 5, a signal conditioning module 9, a signal acquisition module 10, a metal shielding cover 7, a left sealing ring 2 and a right sealing ring 8;
The insulating tube 6 is placed horizontally and parallel to the left-right direction and is made of PTFE; the wall thickness of the insulating tube 6 is 2mm, the wall thickness of the metal shielding cover 7 is 4mm, and the outer diameter of the insulating tube 6 is 14mm;
The metal shielding cover 7 is sleeved on the insulating tube 6 and is in sealing connection with the insulating tube 6 through the left sealing ring 2 and the right sealing ring 8;
The left annular electrostatic induction electrode 3, the arc-shaped electrode 4 with the radian theta of pi/2 rad and the right annular electrostatic induction electrode 5 are all positioned in the metal shielding cover 7 and are sleeved on the insulating tube 6 from left to right in sequence, the distances between the arc-shaped electrode 4 and the left annular electrostatic induction electrode 3 and between the arc-shaped electrode 4 and the right annular electrostatic induction electrode 5 are all 6mm, the outer diameters are all 15mm, the lengths along the left-right direction are all 10.5mm, the maximum outer diameter of the whole oil liquid sensor is 28mm, and the lengths along the left-right direction are 70mm;
The signal conditioning module 9 is connected with the left annular electrostatic induction electrode 3 and the right annular electrostatic induction electrode 5 at the same time, and the signal conditioning module 9 is composed of a fringe capacitance detection circuit and a charge amplifier circuit and is used for conditioning signals on the left annular electrostatic induction electrode 3 and the right annular electrostatic induction electrode 5;
The signal acquisition module 10 adopts a high-speed data acquisition card NI USB9234 (manufacturer is national instrumentation company, USA) for acquiring signals output by the signal conditioning module 9, the data acquisition system is developed based on a Ni LabView2017 software platform, after a corresponding driver program is downloaded by a official network, the nodes in DAQmx sub-selection boards are used for completing the programming of real-time signal acquisition, the front panel is shown in FIG. 9, and the whole flow chart is shown in FIG. 8.
Example 2
A full-flow online oil characteristic monitoring method comprises the following specific steps:
(1) The oil sensor of the embodiment 1 is arranged on a main oil path of a mechanical lubrication system circulation loop, oil in the mechanical lubrication system circulation loop is controlled to flow through an insulating tube of the oil sensor, and an initial excitation voltage (the value is 5V) is continuously applied to an arc electrode;
As shown in fig. 1 and 3, in this process, a fringe capacitance signal a and a static induction signal c are generated on the left annular static induction electrode 3, and a fringe capacitance signal b and a static induction signal d are generated on the right annular static induction electrode 5;
(2) The signal conditioning module 9 performs signal conversion and amplification processing of "capacitance-voltage" on the fringe capacitance signal a and the fringe capacitance signal b by using a fringe capacitance detection circuit (the circuit diagram of which is shown in fig. 6) to obtain a voltage signal e, and performs signal conversion and amplification processing of "charge-voltage" on the electrostatic induction signal c and the electrostatic induction signal d by using a charge amplifier circuit (the circuit diagram of which is shown in fig. 7) to obtain a voltage signal f;
The edge capacitance detection circuit consists of an alternating current bridge module, an operational amplifier module, a phase-sensitive demodulation circuit module (the main module is an AD734AQ chip) and a low-pass filter circuit module (the main module is an AD8051AR chip);
the connection relation of each module in the fringe capacitance detection circuit is as follows:
The input end of the alternating current bridge module is connected with the left annular electrostatic induction electrode 3 and the right annular electrostatic induction electrode 5, the change value of the fringe capacitance signal a on the left annular electrostatic induction electrode 3 and the fringe capacitance signal b on the right annular electrostatic induction electrode 5 is converted into the change value of voltage, and the output ends (2 and 4 ends) of the alternating current bridge module are connected with the input end of the operational amplifier module;
The operational amplifier module converts the differential voltage into single-ended voltage to be output, and the output end of the operational amplifier module is connected with the input end (W) of the phase-sensitive demodulation circuit module;
the phase-sensitive demodulation circuit module divides the voltage signal into a direct current component and a high-frequency alternating current component which are related to the amplitude and the phase, and the output end of the phase-sensitive demodulation circuit module is connected with the input end of the low-pass filter circuit module;
The low-pass filter circuit module filters the high-frequency useless alternating current component demodulated by the AD734AQ chip multiplier to finally obtain a voltage signal e;
the working principle of the fringe capacitance detection circuit is as follows:
The alternating current bridge module monitors the capacitance of the fringe capacitor, the measured fringe capacitor (impedance) is placed on one bridge arm of the alternating current bridge module, the adjustable reference impedance is placed on the other adjacent bridge arm, the sinusoidal signal A 1 sinωt(A1 is the amplitude of the excitation signal, ω is the angular frequency, and t is the time) is applied to the 1 end and the 3 end of the alternating current bridge module, the alternating current bridge module reaches the initial balance state by adjusting the reference impedance R a, and the balance condition of the alternating current bridge module is as follows: Wherein Z d represents the impedance of the measured fringe capacitance, R a represents an adjustable reference impedance, and R b、Rc is a fixed impedance with a value of R 0;
When the abrasive particles pass through the electrodes, the fringe electric field between the electrodes is changed, namely, the value of the fringe capacitance is changed, so that the ac bridge module is changed from the balanced state to the unbalanced state, and a potential difference U 24 is generated between the two ends of the ac bridge modules 2 and 4, which is expressed by the following formula:
Wherein U 12 is the voltage between the 1 end and the 2 end, U 14 is the voltage between the 1 end and the 4 end, U i is the input excitation voltage of the detection circuit, C d is the nominal value of the fringe capacitance, and j is a plurality;
After the ac bridge module successfully converts the values of the two values C 21 and C 22 of the fringe capacitance signals into voltage changes, the next module is required to convert the differential voltage into single-ended output so as to continue detection and processing, where R 21＝R22,R23＝R24, after the 2 and 4 ends of the ac bridge module are connected, finally outputs a single-ended signal, and the expression is as follows:
Wherein U OUT is the output voltage of the operational amplifier module, U IN is the input voltage of the operational amplifier module, and R 23、R21 is the conditioning resistor;
an AD734AQ chip and an AD8051AR chip are respectively used as core parts of a phase-sensitive demodulation circuit module and a low-pass filter circuit module; the AD734AQ chip analog multiplier chip is provided with three pairs of differential input ends (X 1、X2、Y1、Y2、Z1、Z2), input ends (W), denominator control units (U 0、U1、U2, DD and ER) and positive and negative power supply ends (VP and VN), after X, Y, U enters a high-precision multiplication core, the output is added with Z and then is output through an operational amplifier in the AD734AQ chip, and the specific open-loop output is represented by the following formula:
Wherein, A 0 represents the open loop gain of the operational amplifier in the AD734AQ chip, and the closed loop system is formed after the connection of W and Z 1, and the output is:
In order to ensure that the multiplier formed by the AD734AQ chip can have stable system gain, the built-in 10V denominator voltage of the AD734AQ chip, namely U 0、U1、U2, is grounded, and then the output is as follows:
In the phase-sensitive demodulation circuit module, after X 1、X2、Z2 is grounded, the final output after demodulation by the multiplier of the AD734AQ chip is as follows:
When the X 1 is connected with the sine signal of the alternating current bridge module, the Y 1 is connected with the output signal conditioned by the operational amplifier
U OUT, namely: x 1＝A1 sinωt,Y1＝A2 sin (ωt+Φ) to obtain
Wherein A 1 is the amplitude of the excitation signal, ω is the frequency of the sine wave, A 2 is the amplitude of the sine wave conditioned by the AC bridge and the operational amplifier, and Φ is the phase angle between the conditioned output signal U OUT and the excitation signal;
From this, the signal is divided into DC components that are amplitude and phase dependent And a high frequency alternating current componentTwo parts;
the low-pass filter circuit module taking the AD8051AR chip as the core part is adopted to filter the high-frequency useless alternating current component demodulated by the AD734AQ multiplier, and finally the voltage output is obtained
The charge amplifier circuit consists of a sensor interstage capacitor C a, a capacitor C c of a sensor transmission cable, an input cable leakage conductance G c, an input capacitor C i of a charge amplifier, an input conductance G i of the charge amplifier, a feedback capacitor C f of the charge amplifier, a feedback conductance G f of the amplifier and an operational amplifier module;
The connection relation of each device in the charge amplifier circuit is as follows: the induced charge value Q is added into a circuit as a charge source, and is connected in parallel with C a、Cc、Gc、Ci、Gi to obtain U d, namely, differential voltage generated at the inverting input end of the operational amplifier module at the moment, and C f、Gf is connected in parallel with the operational amplifier module;
the working principle of the charge amplifier circuit is as follows:
The charge amplifier can amplify and convert electrostatic induction signals c and d generated by electrostatic induction on the surfaces of the left annular electrostatic induction electrode and the right annular electrostatic induction electrode, and finally output and convert the signals into voltage signals f, so that signal conversion and amplification treatment of charge-voltage are realized;
the voltage signal f output by the charge amplifier has the expression: Wherein C f is the feedback capacitance of the charge amplifier, Q is the induction charge generated by the static induction of the surface of the left annular static induction electrode or the right annular static induction electrode due to the abrasive particles flowing through the electrodes; c a is the sensor inter-stage capacitance, Q a is the charge charged into C a at this time; C c is the capacitance of the sensor transmission cable, Q c is the charge charged into C c at this time, G c is the input cable drain conductance; C i is the input capacitance of the charge amplifier, Q i is the charge charged into C i at this time, G i is the input conductance of the charge amplifier; u d is the differential voltage generated at the inverting input of the operational amplifier module at this time; C f is the feedback capacitance of the charge amplifier, the voltage applied across C f is the difference between U d and the output voltage U o, Q f is the charge now charged to C f, C f is the feedback conductance of the amplifier; the open loop coefficient of the operational amplifier module is A;
The specific derivation process of the expression of the voltage signal f output by the charge amplifier is as follows: u 0＝-A×Ud is known from the inverted input voltage, and therefore the voltage applied across C f is: u cf＝Ud-(-A×Ud)＝Ud × (1+a), assuming that the resistance of the feedback resistor R f is infinite, q=u×c is available, and Q＝Qa+Qc+Qi+Qf＝Ud×(Ca+Cc+Ci+(1+A)×Cf), is therefore And because U 0＝-A×Ud is available
Since a portion of a small order of magnitude can be ignored within the range of accuracy, it can be considered that: namely, converting the electrostatic induction signal c and the electrostatic induction signal d into a voltage signal f through a charge amplifier;
(3) The signal acquisition module acquires a voltage signal e and a voltage signal f;
(4) Processing the voltage signal e and the voltage signal f to obtain oil characteristics;
The oil characteristics comprise abrasive particle characteristics, the change value of the oil temperature before and after the oil enters the insulating tube 6 and the water content of the oil;
The calculation formula of the change value of the oil temperature before and after the oil enters the insulating tube 6 is as follows:
Wherein Δt represents a change value of oil temperature before and after oil enters the insulating tube 6 in units of ℃ and C 21 represents a value of fringe capacitance signal a in units of pf, C 22 represents a value of fringe capacitance signal b in units of pf, L represents a value of length of the left annular electrostatic induction electrode 3 in units of mm in the left-right direction, θ represents a value of radian of the arc electrode 4 in units of rad, γ represents an edge proportionality coefficient, ε t0 represents an oil dielectric constant at the oil temperature before the oil enters the insulating tube 6, and α ε represents a temperature coefficient of the dielectric constant;
When the formula is calculated, only numerical values are substituted, and units are not substituted;
The method for obtaining the water content of the oil liquid comprises the following steps: the method comprises the steps of obtaining a change value A of a dielectric constant caused by moisture and abrasive particles flowing through an electrode before and after oil enters an insulating tube 6 according to a voltage signal e, obtaining a change value B of the dielectric constant caused by the abrasive particles flowing through the electrode before and after oil enters the insulating tube 6 according to a voltage signal f, subtracting the change value B of the dielectric constant from the change value A of the dielectric constant to obtain a change value C of the dielectric constant before and after oil enters the insulating tube 6, and finally obtaining the water content of the oil according to the change value C of the dielectric constant.
In order to verify the accuracy of the monitoring method of the present invention, the following experiments were now performed:
First, the temperature sensor and the device of example 1 were simultaneously placed in a refrigerator to bring both to 2 deg.c:
Then, the device of the embodiment 1 is placed in a constant temperature box at 25 ℃, and the full-flow online oil characteristic monitoring method of the embodiment 2 is adopted to monitor the temperature of the simulated oil, wherein the relationship between the fringe capacitance signal and the oil temperature is shown in figure 10 after the oil temperature value obtained by converting the measured fringe capacitance signal in the monitoring process;
The temperature sensor is placed in an incubator at 25 ℃ and then the temperature of the simulated oil liquid measured by the temperature sensor is recorded;
finally, comparing the temperatures obtained by the two methods, as shown in fig. 11 and fig. 12, it can be seen from the figures that the temperature change of the simulated oil measured by the invention is basically consistent with the temperature change measured by the temperature sensor, so that the temperature change of the simulated oil measured by the invention is accurate.
Claims (9)
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| CN121409838A (en) * | 2025-12-29 | 2026-01-27 | 上海工程技术大学 | A method for monitoring abrasive particles in lubricating oil based on an electrostatically coupled edge electric field sensor |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN121409838A (en) * | 2025-12-29 | 2026-01-27 | 上海工程技术大学 | A method for monitoring abrasive particles in lubricating oil based on an electrostatically coupled edge electric field sensor |
| CN121409838B (en) * | 2025-12-29 | 2026-03-24 | 上海工程技术大学 | Lubricating oil abrasive particle monitoring method based on electrostatic coupling fringe electric field sensor |
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