RU2361209C2 - Method of effective control of oil decomposition and device to this end - Google Patents

Abstract

FIELD: physics; measurement.

SUBSTANCE: invention relates to measuring techniques. Control of oil decomposition is done based on varying the test parametre of working oil relative that of clean oil. The test parametre is calculated using fluorescence intensity of oil, simultaneously measured in three spectral ranges and two operating spectral ranges are used, in which intensity values are greater than in the third. The device has a case in which there is an optical window, and a receiving-transmitting unit, in which are fitted an optical emitter and receiver with a measuring photodetector. The measuring photodetector is a colour sensor, which allows for simultaneous measurement of fluorescence intensity of oil in three spectral ranges.

EFFECT: increased sensitivity and reliability of control.

5 cl, 6 dwg

Description

The invention relates to the field of engineering and can be used to quickly evaluate the health of oil, in particular hydraulic, transmission, motor and transformer, by the degree of its oxidation with a view to timely replacement.

One of the main factors in the deterioration of the working properties of oil is its oxidation, due to the reactions of free radicals, which accelerate in the presence of metals and with increasing temperature. Oxidation of the oil leads to an increase in viscosity, the formation of acids that cause corrosion of metal parts. The use of such an oil leads to intense wear and premature failure of the mechanism. Therefore, to increase the life of the machines, it is necessary to control the quality of the oil used with a view to its timely replacement.

Oil analysis in order to determine its working properties is widely used in laboratories of industrial and transport enterprises.

Known methods commonly used in laboratory conditions for evaluating oil oxidation are the standard method for determining the total acid number and the method of infrared Fourier spectroscopy.

So, the indicator of oil aging due to oxidation according to the standard method / GOST 11362-96. Petroleum products and lubricants. The number of neutralization. The method of potentiometric titration / is characterized by the total acid number, which is measured by titration of an oil sample with an alcoholic solution of potassium hydroxide (KOH) potentiometrically. As oil oxidizes during operation, the total acid number (TAN) increases, indicating oil aging, which is used as a criterion for determining when to change the oil.

Another well-known method for determining the degree of oxidation of oil is the method of molecular infrared Fourier spectroscopy, the principle of which is based on the fact that individual molecules absorb optical radiation at characteristic wavelengths (resonant frequencies). The resonant frequencies of the molecules are due to the presence of molecular characteristic groups consisting of two or more connected atoms. The oxidation of the oil is accompanied by the formation of functional groups having resonance absorption at a frequency of 1740 cm ^-1 / Mark Barnes, Nona Corporation, "The Lowdown on Oil Breakdown". Practicing Oil Analysis Magazine. May 2003 /.

Despite the large amount of information obtained using infrared Fourier spectrometry, it is not always reliable enough, since most of the oils used are a complex mixture of various molecules, including molecules of the base oil base, additives, oil aging products, wear particles and dirt and as a consequence, the infrared spectrum of the oil is usually complex and can be interpreted with some degree of uncertainty.

Laboratory tests usually have high information content, sensitivity and accuracy, however, they require significant time costs and the analysis results arrive with a large time delay. In addition, when sampling an oil, the problem arises of ensuring its representativeness. Significantly hampers the widespread use of laboratory methods and their high cost. In order to reduce the time between sampling and the result of analysis, new methods are currently being developed for the operational monitoring of oils in real time and the devices that implement these methods are built into the lubrication system of machines.

Known electrical methods and devices for continuous monitoring of the state of oil, working in real time and combining low cost analysis and sufficient reliability for the optimal use of lubricant, timely replacement and ensure reliable operation of the mechanism.

So, it is known a device for monitoring the quality of oil / US Patent No. 6459995, IPC: G01N 031/00, publ. 10/01/02 /, based on the measurement of changes in the dielectric constant of the oil. The device contains a capacitive sensor immersed in oil, which is an element of the oscillatory circuit containing an LC or crystal oscillator. The output signal of the oscillatory circuit depends on the dielectric loss tangent of the oil, which varies with the change in the acidity of the oil. Thus, the output signal carries information about the degree of oxidation of the oil. The disadvantage of this device is that the dielectric constant of the oil, and therefore the output signal, depends not only on the acidity of the oil, but also on the water content, the degree of contamination of the oil by mechanical particles, which makes it impossible to establish the main factor that caused the signal to change.

Also known is a method and device for evaluating the quality of oil / US Patent No. 5789665, IPC: G01N 027/26; G01N 033/30, publ. 08/04/98 / based on the measurement of electrical resistance. The device contains a single-layer matrix of ion-charged polymer balls located between two permeable electrically conductive surfaces so that when immersed in oil, it passes through the matrix of balls. The attraction of the charged groups of polymer balls changes when the oil changes from a non-polar to a polar (oxidized) state, which causes an electrical resistance of the matrix.

The main disadvantages of this device are its low sensitivity and the need to replace the matrix of polymer balls with each oil change.

In addition to electrical, optical, in particular fluorescent, real-time oil quality control methods are also known, designed to increase sensitivity by reducing electrical noise.

The main problem of fluorescence methods based on recording the fluorescence intensity of the oil is the effect of high optical density (strong absorption) of the oil on the fluorescence intensity. To solve this problem, special methods are used to measure the oil fluorescence parameters in devices for monitoring the working properties of oil.

Thus, the fluorescence method is known / US Patent No. 6633043, IPC: G01N 021/64, publ. 10/14/03 /, based on time-resolved fluorescence spectroscopy, for controlling the aging of mineral lubricating and transformer oils, not requiring consideration of their optical density. The method is based on the analysis of time-resolved spectra of fresh and working oils and includes the following steps: irradiation of the tested oil sample with a UV laser pulse; measuring the fluorescence spectra of oil using a temporary selection technique to obtain a time-resolved spectrum; construction of normalized time-resolved spectra and comparison of the obtained spectra. The measuring device contains a pulsed UV laser, the radiation from which is directed by means of a mirror onto a cuvette with a test oil. The fluorescence flux using quartz lenses is focused on the entrance slits of the monochromator, in the output slots of which a photomultiplier is installed to record the fluorescence signal. The signal from the output of the photomultiplier is fed through an integrator with a narrow-band filter to a computer for further processing. The disadvantage of this method and device is that they are very difficult for operational control, which involves a built-in lubrication line or a portable device. In addition, the implementation of the method requires expensive equipment.

The prototype of the invention is a device and a method for determining oil oxidation in real time, based on measuring the change in the fluorescence intensity of the oil, application No. 20050088646 for US patent, IPC: G01N 021/00, publ. 04/28/05 / during its oxidation. A method for the operational control of oil oxidation consists in sending a beam of optical radiation that stimulates the fluorescence of the oil to the test oil, measuring the fluorescence of fresh oil, calculating the diagnostic parameter, measuring the fluorescence intensity during the operation of the oil, calculating the diagnostic parameter and changing the diagnostic parameter of the operating relatively fresh oils judge the degree of oxidation of the oil.

The disadvantages of the prototype are, firstly, the lack of sensitivity and reliability of control of the degree of oxidation of the oil, since the fluorescence intensity and the diagnostic parameter used depend on the temperature, in addition, it is necessary to take into account the influence of the optical density of the oil on the diagnostic parameter. Secondly, the need to use a second transceiver assembly and a reflecting mirror to estimate the optical density of the oil complicates the design and increases the overall dimensions of the device, which is an important aspect for devices built into the lubrication system of the equipment.

The objective of the invention is to increase the sensitivity and reliability of the operational control of oil oxidation by using a diagnostic parameter that is independent of the optical density and temperature of the oil, as well as improving the design of the device in order to increase sensitivity, simplify the design and reduce its size.

The problem is solved in that the known method for the operational control of oil oxidation consists in sending a beam of optical radiation that excites oil fluorescence to the test oil, measuring the fluorescence of fresh oil, calculating the diagnostic parameter, measuring the fluorescence intensity during the operation of the oil, and calculating the diagnostic the parameter and judging by the change in the diagnostic parameter of the working oil relative to the fresh one, they judge the degree of oxidation of the oil, changed in conditions for measuring the fluorescence intensity of oil and is supplemented by a new set of operations. The change in the conditions for measuring the fluorescence intensity of the oil is that the fluorescence intensity is measured simultaneously in three spectral ranges. A new set of operations is that when testing fresh oil from three controlled spectral ranges, two workers are determined in which the intensities are greater than in the third, and the diagnostic parameter F is calculated by the formula

Where

J _Δλdl - the value of the fluorescence intensity, measured in a longer wavelength working spectral range,

J _Δλcor is the value of fluorescence intensity measured in the shorter wavelength working spectral range.

In the known method, the quantum parameter of fluorescence serves as a diagnostic parameter, which is determined by the integrated fluorescence intensity, which depends on the oxidation of the oil. The quantum yield of fluorescence depends on the temperature of the oil and, in addition, when calculating it, it is necessary to take into account the optical absorption (optical density) of the oil / Levshin L.V., Saletsky A.M. Luminescence and its measurement: Molecular luminescence. - M.: Publishing House of Moscow State University; 1989 .-- 272 p. /. Figure 1 shows the change in the fluorescence intensity spectra measured on a fluorometer (Model K2, ISS Co., USA) of fresh hydraulic oil and two samples (A and B) of working oil, and the operating time of oil B is longer than oil A. In the present method the diagnostic parameter is the ratio of the fluorescence intensity of the oil in the range of longer wavelengths of the fluorescence spectrum to the fluorescence intensity of the oil in the range of shorter wavelengths of the fluorescence spectrum. Those. the diagnostic parameter characterizes the shift in the fluorescence intensity of the oil in the longer wavelength region of the spectrum. The shift of the fluorescence intensity to the long-wavelength region is determined by the oxidation of the oil and does not depend on its temperature and optical density.

Changing the measurement conditions and introducing a new set of operations makes it possible to use a diagnostic parameter independent of the temperature and optical density of the oil for operational monitoring of oil oxidation, resulting in a decrease in the minimum detectable change in the diagnostic parameter, i.e. increases the sensitivity and reliability of control.

To implement the proposed method, there is provided a device comprising a housing with an optical window fixed therein and a transceiver assembly in which an emitter and an optical radiation receiver with a measuring photodetector are installed, and according to the invention, the measuring photodetector, which is an element of the optical radiation receiver, is a color sensor, allowing to simultaneously measure the fluorescence intensity of the oil in three spectral ranges and calculate independent of temperature and optical chemical density of oil is a diagnostic parameter characterizing the shift of the fluorescence spectrum. The use of such a measuring photodetector eliminates the need for a second transceiver assembly and a reflective mirror. This simplifies the design and reduces the overall dimensions of the device. In addition, to ensure maximum reception of fluorescence emission of oil by the optical radiation receiver, the thickness of the optical window and the relative position of the emitter, the optical window and the optical radiation receiver satisfy the following relation

Where

L is the distance between the points of intersection of the optical axes of the emitter and the receiver of optical radiation with the input surface of the optical window,

t _UV - the size of the radiating area of the emitter,

t _DC - the size of the receiving platform of the receiver of optical radiation,

θ _UV is the angle between the optical axis of the optical window and the optical axis of the emitter,

θ _DC - the angle between the optical axis of the optical window and the optical axis of the receiver of optical radiation,

φ _UV , φ _DC - the aperture angle of the emitter and the input aperture angle of the receiver of optical radiation, respectively,

n _in - refractive index of air,

n _o is the refractive index of the material of the optical window.

The above ratio is obtained from the condition of maximum reception of oil fluorescence radiation by the optical radiation receiver, which is illustrated in Figs. 2, 3. It is necessary to coordinate the aperture of the emitter and receiver so that the entire radiation beam of the emitter that excites fluorescence, when it enters the oil, is covered by the aperture of the receiver, those. so that the extreme rays of the aperture angles of the emitter and receiver intersect when they enter the oil. This condition is satisfied by using an optical window of such a thickness that the extreme rays of the aperture angles intersect on the window surface in contact with the oil (at point A, FIGS. 2, 3). Figure 3 presents a special case when θ _UV = θ _DC = 0 and L = t _UV = t _DC , then

Additionally, a feedback photodetector is installed in the transceiver assembly of the device, which measures the radiation intensity of the emitter, and its output signal is used in the feedback circuit to stabilize the radiation of the emitter, which reduces the fluctuation of the measuring signals and, accordingly, increases the sensitivity of the device.

In addition, an oleophobic coating is applied to the surface of the optical window in contact with the oil, which prevents surface contamination, which increases the reliability and sensitivity of the device. As such a coating, for example, Novec Coating EG-1720 coating ('3M' Co., USA) can be used.

The invention is illustrated by drawings, which depict:

figure 1 - change in the fluorescence intensity spectra measured on a fluorometer (Model K2, ISS Co., USA) of fresh hydraulic oil and two samples (A and B) of working oil

figure 2, 3 illustrate the relationship between the thickness of the optical window, the apertures of the emitter and receiver of optical radiation and the relative positions of the emitter, optical window and receiver of optical radiation

figure 4 - the design of the device for implementing the proposed method for the operational control of oil oxidation, in which the emitter consists of an optical radiation source and optical fiber, and the optical radiation receiver includes a measuring photodetector and an optical fiber;

figure 5 - the design of the device for implementing the proposed method for the operational control of oil oxidation, in which the emitter is a source of optical radiation, and the optical radiation receiver is a measuring photodetector.

6 illustrates the use of the proposed method and device for monitoring the oxidation of hydraulic oil: a change in the diagnostic parameter and the total acid number from the time of operation.

The main nodes of the device that implements the method of operational control of oil oxidation are shown in figure 4. The device comprises a housing 12, an optical window 9 and a transceiver assembly, a protective cover 4, a mounting plate 16, and an electrical cable 15. An optical window 9 is installed in the housing 12 using a nut 8 and an O-ring 11. The transceiver assembly includes bushings 3, 13, in which are installed: a radiator, an optical radiation receiver and a feedback photodetector 2. The emitter consists of an optical radiation source 1, an optical fiber 17 and a spherical lens 5. mounted between them through the adapter ring 6. In this case, the input end optical fiber 17 is turned to the radiation source 1, and the output to the optical window 9. A spherical lens 5 is used to focus the optical radiation of the source 1 on the input end of the optical fiber 17. The optical radiation receiver contains a measuring photodetector 14 and an optical fiber 10, the output end of which is turned to the optical window 9, and the input to the measuring photodetector 14. A radiation source, a spherical lens, a measuring photodetector and a feedback photodetector are installed in the sleeve 3 of the transceiver evil. Optical fibers 10, 17 are installed in the sleeve 13 of the transceiver assembly, which is connected to the sleeve 3. The electrical terminals of the radiation source, the measuring photodetector and the feedback photodetector are output to the mounting plate 16, mounted on the sleeve 3 and connected by an electric cable 15 to an electronic unit (not shown ) To protect against mechanical damage and shielding from electrical interference, a protective cover 4 is used, fixed by screws on the sleeve 13.

Figure 5 shows a design variant of the device in which the emitter and the receiver of optical radiation do not contain optical fibers, but are a radiation source 1 and a measuring photodetector 14. Here, the housing 12 simultaneously acts as a protective cover, and the optical window 9 is glued into the housing 12.

As a radiation source, the proposed device uses a source of such radiation, which excites the fluorescence of the oil, i.e. with a wavelength in the range of 350-450 nm (for example, a UV diode. LED3-UV-395-30 from Bivar Inc., USA). The measuring photo receiver is a color sensor that allows you to simultaneously measure the fluorescence intensity of the oil in three spectral ranges, in particular, in “red”, “green” and “blue”. Such a receiver can be, for example, Color Sensor MCS3AT / MCS3BT (MAZeT GmbH, Germany) and Color Sensor TCS230 (Texas advanced optoelectronic solutions Inc., USA).

The device using the sealing ring 7 is installed in the oil circulation system or in the oil tank.

The device operates as follows. The beam of optical radiation from the emitter through the optical window 9 is directed to the test oil. Moreover, in the irradiated volume of oil, its fluorescence is excited. The fluorescence radiation flux passing through the optical window 9 enters the optical radiation receiver. When filling the lubrication system with fresh oil, the fluorescence intensity (J _R , J _G and J _B ) is measured simultaneously in three spectral ranges - red "R", green "G" and blue "B" - using a color sensor used as a measuring photodetector 14. Then, from the three spectral ranges, two operating ranges Δλ _dl and Δλ _cor are determined, in which the intensities are greater than in the third. The diagnostic parameter F used to control oil oxidation is calculated by the formula

Where

J _Δλdl - the value of the fluorescence intensity, measured in a longer wavelength working spectral range,

J _Δλcor is the value of fluorescence intensity measured in the shorter wavelength working spectral range.

During the operation of the equipment, oil oxidation occurs, which is accompanied by a shift in the fluorescence spectrum to the long-wavelength region and an increase in J _Δλ for relatively J _Δλcor , i.e. an increase in the diagnostic parameter F. Thus, an increase in the diagnostic parameter indicates an increase in the degree of oxidation of the oil. When parameter F is increased to a preset critical value, a warning signal about the need for an oil change is triggered.

An example of the implementation of the proposed method and device for monitoring the oxidation of oil MOBIL DTE-24 in a hydraulic system.

так как

В таблице приведены измеренные значения сигналов в трех спектральных диапазонах для свежего масла (время эксплуатации t=0) и для масла, работавшего в гидравлической системе в течение времени t1 и t2 и соответствующие значения диагностического параметра F. В таблице приведены также значения общего кислотного числа TAN, измеренные стандартным методом (ГОСТ 11362-96. Нефтепродукты и смазочные материалы. Число нейтрализации. Метод потенциометрического титрования) для свежего масла и проб масла, взятых в моменты времени t1 и t2.The device of the structure shown in figure 4, was installed in a tank with oil. The lubrication system was filled with pure MOBIL DTE-24 oil and the oil oxidation control device was turned on. At the output of the color sensor, which was used as the Color Sensor MCS3AT / MCS3BT, using the microcontroller, three signals were simultaneously recorded (U _R = 99 mV, U _G = 245 mV and U _B = 296 mV), corresponding to the fluorescence intensity of the oil (J _R , J _G and J _B ) in the red “R”, green “G” and cyan “B” spectral range. Further signal processing was also performed using a microcontroller, namely, it was determined that the minimum value of the three signals (U _R , U _G and U _B ) is the signal in the red spectral range, i.e., the working spectral ranges are green and blue, and J _{Δλ for} = J _G , J _Δλcor = J _B. Therefore, the diagnostic parameter F in the evaluation of the oxidation of oil MOBIL DTE-24 was determined as the ratio

as

The table shows the measured signal values in three spectral ranges for fresh oil (operating time t = 0) and for oil that has been working in the hydraulic system for times t1 and t2 and the corresponding values of the diagnostic parameter F. The table also shows the values of the total acid number TAN measured by the standard method (GOST 11362-96. Petroleum products and lubricants. Neutralization number. Potentiometric titration method) for fresh oil and oil samples taken at time t1 and t2.

Table Oil operating time t = 0 t1 t2 U _R , mV 99 90 85 U _G , mV 245 174 140 U _B , mV 296 138 75 F 0.83 1.26 1.87 TAN, mg KOH / g 0.9 1,1 1.7

Figure 6 shows the change in the diagnostic parameter and the total acid number during operation and the critical value of the diagnostic parameter.

The values of the diagnostic parameter F were displayed on the indicator of the electronic unit. As can be seen from Fig.6, the values of the diagnostic parameter F during the operating time on the graph did not exceed the critical value and the warning signal about the need to change the oil (indicator LED of the electronic unit) did not work.

The above example shows that the proposed diagnostic parameter F allows for operational monitoring of oil oxidation. The correlation of the parameter F with the total acid number indicates a high reliability of the proposed method and device.

Claims (5)

1. The method of operational control of oil oxidation, namely, that a beam of optical radiation that excites oil fluorescence is directed to the test oil, the fluorescence intensity of fresh oil is measured, a diagnostic parameter is calculated, the fluorescence intensity is measured during oil operation, a diagnostic parameter is calculated and the change the diagnostic parameter of the working oil relative to fresh judge the degree of oxidation of the oil, characterized in that the fluorescence intensity is changed yayut simultaneously in three spectral ranges and for testing of fresh oil is determined by two operating spectral range, in which the values of intensities larger than the third, and diagnostic parameter F is calculated according to the formula

where J _Δλdl is the value of the fluorescence intensity, measured in a longer wavelength working spectral range,
J _Δλcor is the value of fluorescence intensity measured in the shorter wavelength working spectral range. 2. A device for the operational control of oil oxidation, comprising a housing with an optical window fixed therein and a transceiver assembly in which an emitter and an optical radiation receiver with a measuring photodetector are installed, characterized in that the measuring photodetector is a color sensor that simultaneously measures the intensity fluorescence of oil in three spectral ranges. 3. The device according to claim 2, characterized in that the thickness of the optical window is determined by the formula

Where

L is the distance between the points of intersection of the optical axes of the emitter and the receiver of optical radiation with the input surface of the optical window,
t _UV - the size of the radiating area of the emitter,
t _DC - the size of the receiving platform of the receiver of optical radiation,
θ _UV is the angle between the optical axis of the optical window and the optical axis of the emitter,
θ _DC - the angle between the optical axis of the optical window and the optical axis of the receiver of optical radiation,
φ _UV , φ _DC - the aperture angle of the emitter and the input aperture angle of the receiver of optical radiation, respectively,
n _In - refractive index of air,
n _o is the refractive index of the material of the optical window. 4. The device according to claim 2, characterized in that a feedback photodetector is additionally installed in the transceiver assembly. 5. The device according to claim 2, characterized in that an oleophobic coating is applied to the surface of the optical window in contact with the oil.

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