A method for simultaneous online detection of grease distribution and oil separation

Abstract

This invention belongs to the field of lubrication technology, specifically relating to a method for simultaneous online detection of grease distribution and oil separation. In this invention, suitable fluorescent agents are selected: methylpyrrole is soluble only in the base oil phase, and coumarin is soluble only in the thickener phase. The distribution of the base oil is characterized by detecting the fluorescence intensity of methylpyrrole, and the distribution of the thickener is characterized by detecting the fluorescence intensity of coumarin. Methylpyrrole and coumarin can be excited simultaneously by the same light source, thus generating fluorescence synchronously. The wavelength difference between the fluorescence emission peaks of methylpyrrole and coumarin is significant; therefore, the two fluorescence signals can be separated using a spectrometer, allowing two receivers to simultaneously receive both fluorescence signals.

Description

Technical Field

[0001] This invention belongs to the field of lubrication technology, specifically relating to a method for simultaneous online detection of grease distribution and oil separation. Background Technology

[0002] In industrial applications, approximately 80% of rolling bearings use grease as a lubricant. Grease generally consists of a base oil and a thickener. Compared to lubricating oil, grease is more convenient to use and less expensive. A certain mass of grease is filled into the bearing, and as the bearing rotates, the grease distributes to the surfaces of all bearing components. Near the contact area between the rolling elements and the inner and outer rings, the grease enters the contact area due to entrainment, forming a lubricating oil film that separates the rolling elements from the inner and outer rings, preventing dry contact and achieving lubrication. Simulation experiments based on ball-disc point contact suggest that at low speeds, grease can directly enter the contact area to form a lubricating oil film, while at medium to high speeds, the grease precipitates base oil under compression and shearing action. The base oil then enters the contact area to form a lubricating oil film, while the thickener acts as an oil reservoir, continuously precipitating base oil to supply lubrication. This indicates that grease not only migrates and changes its distribution within rolling bearings but also precipitates lubricating oil. Understanding the distribution and oil precipitation changes of grease is crucial for accurately obtaining the lubrication performance within rolling bearings.

[0003] Commonly used measurement methods for studying changes in grease distribution and oil separation include:

[0004] Method 1: Offline detection of grease separation: This mainly includes Fourier transform infrared spectroscopy (FTIR). After running for a period of time, the machine is stopped, and Fourier transform infrared spectroscopy is used to detect the residual grease near the raceway. This reveals that due to shearing action in the contact area, the base oil and thickener separate in the outlet area. This method can accurately detect changes in grease separation, but it requires offline detection and cannot obtain the actual distribution under operating conditions.

[0005] Method 2: Online detection of grease distribution, mainly including direct optical observation, fluorescence calibration, and particle image velocimetry. In recent years, thanks to advancements in detection methods and computer technology, researchers have had the opportunity to conduct online dynamic experimental measurements of the oil supply layer distribution in the inlet area. With the aid of a high-speed camera, researchers observed the entire process of thickener entering the contact area using an optical microscope. This demonstrates that optical observation is an important means of elucidating the film-forming mechanism of grease. Particle image velocimetry can reveal the velocity distribution and flow regime of lubricating oil near the inlet area. Fluorescence calibration of the base oil in the grease can obtain the distribution of grease near the contact area under dynamic conditions. While these methods can visually reveal the distribution of grease, they cannot reflect changes in grease separation.

[0006] In conclusion, if a detection method could obtain online information on the distribution and oil separation changes of grease within a rolling bearing, it would overcome the problems of existing methods and provide a more intuitive representation of the grease's lubrication characteristics. This offers a new approach to improving grease distribution in critical bearing components, thereby improving bearing geometry and lubrication parameters, and ultimately extending grease and bearing life. Summary of the Invention

[0007] In view of this, the present invention proposes a method for simultaneous online detection of grease distribution and oil separation. This method is a high-precision dual-calibration fluorescence method for grease, which uses two fluorescent agents to calibrate the base oil phase and thickener phase of the grease separately, so as to realize the separate tracking and quantitative detection of the two-phase flow of grease, thereby obtaining the distribution and oil separation information of grease online at the same time.

[0008] The technical solution of this invention is:

[0009] A method for simultaneous online detection of grease distribution and oil separation, the method comprising the following steps:

[0010] Step 1: Mix the fluorescent agent methylpyrrole, the fluorescent agent coumarin, and the grease to be tested to obtain mixtures of different thicknesses;

[0011] Step two: Illuminate the mixtures of different thicknesses obtained in step one using a light source. The fluorescent agents methylpyrrole and coumarin will produce fluorescence. The fluorescence produced by methylpyrrole is received by camera A, and the gray value obtained by taking a picture with camera A represents the fluorescence intensity produced by methylpyrrole. The fluorescence produced by coumarin is received by camera B, and the gray value obtained by taking a picture with camera B represents the fluorescence intensity produced by coumarin. Thus, a quantitative relationship between the fluorescence intensity produced by methylpyrrole and the thickness of the mixture is obtained. A quantitative relationship between the fluorescence intensity produced by coumarin and the thickness of the mixture is also obtained.

[0012] Step 3: Add the mixture of different thicknesses obtained in Step 1 to the inside of the bearing. Run the bearing and the mixture will be distributed to various positions in the bearing. By detecting the fluorescence intensity of the mixture and according to the quantitative relationship obtained in Step 2, the thickness distribution of the mixture inside the bearing can be obtained. Then, based on the ratio r of the fluorescence intensity of the fluorescent agent methylpyrrole and the fluorescent agent coumarin in the mixture, the oil separation information of the lubricating grease in the mixture can be obtained.

[0013] In step one, the fluorescent agent methylpyrrole dissolves only in the base oil phase of the grease to be tested, and the fluorescent agent coumarin dissolves only in the thickener phase of the grease to be tested.

[0014] In step two, the quantitative relationship is as follows:

[0015] I f(h)=kI0Φ{1-exp[-ε(λ laser )Ch]}

[0016] Among them, I f (h) Fluorescence intensity, I0 is the light source intensity, Φ is the quantum yield, k is the camera's monitoring efficiency, ε(λ) laser ) represents the molar absorptivity of the fluorescent agent to the laser light emitted by the light source, C represents the molar concentration of the fluorescent agent, and h represents the thickness of the mixture;

[0017] In step three, the fluorescence intensity ratio of the fluorescent agent methylpyrrole in the base oil phase and the fluorescent agent coumarin in the thickener phase under bulk conditions is:

[0018] r0 = I A0 / I B0

[0019] Among them, I A0 I represents the fluorescence intensity of the fluorescent agent methylpyrrole in the base oil phase under bulk conditions. B0 The ratio r0 represents the fluorescence intensity of the fluoropolymer coumarin in the thickener phase under bulk conditions. Once the type and concentration of the fluoropolymer are selected, the ratio r0 is a constant.

[0020] Based on the relationship between r and r0, when r is greater than r0, it indicates that the base oil in the grease mixture has separated out; if r equals r0, it indicates that the base oil in the grease mixture has not separated out.

[0021] Beneficial effects

[0022] (1) This invention discloses a method for simultaneous online distribution and oil separation detection of lubricating grease based on dual fluorescence calibration. This method realizes online distribution detection and oil separation detection of lubricating grease, providing an effective means to more intuitively display the lubricating characteristics of lubricating grease.

[0023] (2) This invention achieves separate calibration and simultaneous detection of the base oil phase and thickener phase in lubricating grease by rationally selecting fluorescent agents and a dual-optical-path detection system.

[0024] (3) Compared with existing grease detection methods, this method can detect the distribution and oil separation changes of grease online simultaneously, which will help reveal the lubrication mechanism of grease and guide the precise use of grease.

[0025] (4) In this invention, by selecting suitable fluorescent agents, methylpyrrole is dissolved only in the base oil phase, and coumarin is dissolved only in the thickener phase. The distribution of the base oil is characterized by detecting the fluorescence intensity of methylpyrrole, and the distribution of the thickener is characterized by detecting the fluorescence intensity of coumarin. Methylpyrrole and coumarin can be excited simultaneously by the same light source, thus generating fluorescence synchronously. The wavelength difference between the fluorescence emission peaks of methylpyrrole and coumarin is significant, allowing the two fluorescence signals to be separated using a spectrometer, thereby enabling the synchronous reception of both fluorescence signals using two receivers. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the fluorescence spectra produced by the two fluorescent agents;

[0027] Figure 2 This is a schematic diagram of a dual-path fluorescence system;

[0028] Figure 3 This is a schematic diagram showing the change in the strength ratio of the base oil / thickener two phases at the central cross section. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the figures and examples.

[0030] A method for simultaneous online detection of grease distribution and oil separation, the method comprising the following steps:

[0031] Step 1: The target grease is a lithium-based grease with PAO8 as the base oil. A suitable fluorescent agent is selected. Methylpyrrole, the fluorescent agent, is only soluble in the base oil phase, with an excitation fluorescence peak around 600 nm. Coumarin, the fluorescent agent, is only soluble in the thickener phase, with an excitation peak around 500 nm.

[0032] Step Two: Add the fluorescent agents methylpyrrole and coumarin uniformly to the target grease using mechanical stirring or chemical dissolution. First, dissolve the coumarin in the grease and stir thoroughly. Then, dissolve the methylpyrrole in the grease. Spectrometer analysis shows that the grease at this point produces a fluorescence signal with two peaks. Figure 1 As shown, the two fluorescence peaks are located near 500 nm and 600 nm, respectively, and are clearly separated.

[0033] Step 3: Construct a dual-path fluorescence system, such as... Figure 2 As shown, a 365nm laser light source was used to excite a grease containing two fluorescent agents. The two fluorescent agents emitted fluorescence at two different wavelengths, which were then imaged onto cameras 1 and 2 respectively using a 550nm dichroic filter. The fluorescence signal I received by camera 1 is then... A The fluorescence signal I received by camera 2 represents the distribution information of the base oil phase.B This represents the distribution information of the thickener phase.

[0034] Step 4: Convert the fluorescence intensity signal into film thickness information. In a static state, a grease containing two fluorescent agents is filled between a steel ball and a glass disk of known size. At a certain location, the gap between the ball and the disk is the same as the grease thickness. The dual-optical-path system built in Step 3 is used to detect the grease distribution in this static state, obtaining the fluorescence information at the corresponding location. Thus, a definite relationship between grease thickness and fluorescence intensity can be obtained, expressed in exponential form:

[0035] I f (h)=kI0Φ{1-exp[-ε(λ laser )Ch]}

[0036] Among them, I f (h) Fluorescence intensity, I0 is the light source intensity, Φ is the quantum yield, k is the camera's monitoring efficiency, ε(λ) laser ) represents the molar absorptivity of the fluorescent agent to the laser light emitted by the light source, C represents the molar concentration of the fluorescent agent, and h represents the thickness of the mixture;

[0037] Simultaneously, the fluorescence intensity ratio of the fluorescent agent methylpyrrole in the base oil phase and the fluorescent agent coumarin in the thickener phase under bulk conditions was obtained:

[0038] r0 = I A0 / I B0

[0039] Among them, I A0 I represents the fluorescence intensity of the fluorescent agent methylpyrrole in the base oil phase under bulk conditions. B0 The ratio r0 represents the fluorescence intensity of the fluoropolymer coumarin in the thickener phase under bulk conditions. Once the type and concentration of the fluoropolymer are selected, the ratio r0 is a constant.

[0040] Step 5: Use formula (1) to convert the fluorescence signals received by the two cameras into thickness information, thereby obtaining the thickness information of the two fluorescent agents at different locations, i.e. the distribution information of the grease;

[0041] Step Six: Normalize the fluorescence intensity ratio. Using the ratio r0 of the fluorescence intensity of the two fluorescent agents detected in the bulk grease as a reference, compare the signal intensity ratio r = I of the two fluorescent agents at different locations under online detection conditions. A / I B The fluorescence intensity ratio was compared with that in the bulk phase (r0) to obtain the changes in the fluorescence intensity ratio at different locations, i.e., the changes in the two components within the grease. Figure 3 As shown, under bulk conditions, r0 = 0.3, but near the contact area, r increases and r / r0 approaches 2, indicating that the base oil accumulates more in this area.

Claims

1. A method for simultaneous online detection of grease distribution and oil separation, characterized in that... The steps of this method include: Step 1: Mix the fluorescent agent methylpyrrole, the fluorescent agent coumarin, and the grease to be tested to obtain mixtures of different thicknesses; Step two: Illuminate the mixtures of different thicknesses obtained in step one using a light source. The fluorescent agents methylpyrrole and coumarin will produce fluorescence. The fluorescence produced by methylpyrrole is received by camera A, and the gray value obtained by taking a picture with camera A represents the fluorescence intensity produced by methylpyrrole. The fluorescence produced by coumarin is received by camera B, and the gray value obtained by taking a picture with camera B represents the fluorescence intensity produced by coumarin. Thus, a quantitative relationship between the fluorescence intensity produced by methylpyrrole and the thickness of the mixture is obtained. A quantitative relationship between the fluorescence intensity produced by coumarin and the thickness of the mixture is also obtained. Step 3: Add the mixture obtained in Step 1 to the inside of the bearing, run the bearing, and the mixture will be distributed to various positions of the bearing. By detecting the fluorescence intensity of the mixture and according to the quantitative relationship obtained in Step 2, the thickness distribution of the mixture inside the bearing can be obtained. Then, based on the ratio r of the fluorescence intensity of the fluorescent agent methylpyrrole and the fluorescent agent coumarin in the mixture, the oil separation information of the lubricating grease in the mixture can be obtained. In step two, the quantitative relationship is as follows: I f (h)=kI0Φ{1-exp[-ε(λ laser )Ch]} Among them, I f (h) Fluorescence intensity, I0 is the light source intensity, Φ is the quantum yield, k is the camera's monitoring efficiency, ε(λ) laser ) represents the molar absorptivity of the fluorescent agent to the laser light emitted by the light source, C represents the molar concentration of the fluorescent agent, and h represents the thickness of the mixture; In step three, the fluorescence intensity ratio of the fluorescent agent methylpyrrole in the base oil phase and the fluorescent agent coumarin in the thickener phase under bulk conditions is: r0=I A0 / I B0 Among them, I A0 I represents the fluorescence intensity of the fluoropolymer methylpyrrole in the base oil phase under bulk conditions. B0 The ratio r0 represents the fluorescence intensity of the fluoropolymer coumarin in the thickener phase under bulk conditions. Once the type and concentration of the fluoropolymer are selected, the ratio r0 is a constant. In step three, based on the relationship between r and r0, if r is greater than r0, it indicates that the base oil in the grease in the mixture has precipitated; if r is equal to r0, it indicates that the base oil in the grease in the mixture has not precipitated.

2. The method for simultaneous online detection of grease distribution and oil separation according to claim 1, characterized in that: In step one, the fluorescent agent methylpyrrole dissolves only in the base oil phase of the grease to be tested, and the fluorescent agent coumarin dissolves only in the thickener phase of the grease to be tested.

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