A method for evaluating the dispersion performance of lubricating oil soot

Abstract

This invention discloses a method for evaluating the dispersion performance of soot in lubricating oil, comprising the following steps: 1. Adding soot particles to base oil and stirring evenly to form a soot liquid; 2. Adding the lubricating oil to be tested to a reaction vessel equipped with a viscosity sensing probe and an air delivery tube; 3. Placing the reaction vessel in an oil bath, introducing air from the bottom of the reaction vessel, and slowly adding the soot liquid from step 1 to the reaction vessel using a peristaltic pump; 4. When the kinematic viscosity of the lubricating oil to be tested increases to 200 mmHg... 2 The test is considered complete when the soot dispersion performance of a lubricating oil reaches a certain value per second. This invention relates to the field of lubricating oil analysis and evaluation technology. The method for evaluating the dispersion performance of lubricating oil soot utilizes soot particles generated from the combustion of fuel oil in a soot generator. This method maximizes the replication of the soot generation process in the combustion chamber of an engine during operation. The resulting soot is free of other lubricating oil additives, providing a raw material guarantee for subsequent evaluation of the soot dispersion performance in lubricating oils.

Description

Technical Field

[0001] This invention relates to the field of lubricating oil analysis and evaluation technology, specifically to a method for evaluating the soot dispersion performance of lubricating oil. Background Technology

[0002] High-quality lubricating greases play a vital role in national economic development, often referred to as the "blood" of machinery. They are widely used in the automotive industry, construction machinery, metallurgy and mining, power generation, machine tools, special operations, and transportation. As a primary technology for reducing friction and wear, the quality of lubricating oil directly impacts the reliability, stability, and service life of equipment. With advancements in engine technology and increasingly stringent environmental regulations, countries worldwide have introduced stricter emission standards for motor vehicles. Engine design is trending towards high efficiency, energy saving, and low emissions, and engine manufacturers (OEMs) have adopted new technologies such as delayed fuel injection, exhaust gas recirculation (EGR), and particulate filters. However, under delayed fuel injection conditions, fuel combustion is incomplete, leaving unburned fuel residue on the cylinder walls due to flameout. Furthermore, lubricating oil can enter the combustion chamber through gas leakage, friction from valve stem seals and piston rings, and oil vapor from the cylinder walls and combustion chamber, accumulating over time to form soot. Studies have shown that soot is a mixture of various substances. The formation of soot mainly involves the following four stages of chemical and physical changes: (1) The main components of fuel—low-molecular-weight hydrocarbons—are cracked at high temperatures to generate unsaturated hydrocarbons; (2) Unsaturated hydrocarbons and other substances undergo chemical reactions to form soot precursor particles; (3) Soot precursor particles gradually grow into soot particle cores through surface reactions. After the core particles of soot are formed, they aggregate with molecular clusters such as acetylene and PAH, and the volume and mass of the particles further increase. At the same time, particles aggregate through mutual collisions, reducing the number of particles but increasing their volume; (4) After aggregation, the particles undergo functional group disappearance, cyclization, ring concentration, and ring fusion under dehydrogenation and aromatic hydrocarbon stratification, eventually forming soot particles. The accumulation of large amounts of soot can clog filters, affecting fuel supply, increasing oil viscosity and reducing fluidity. It also exacerbates wear on the engine cylinder liner-piston ring section and the intake and exhaust valve system. Therefore, engine oils are required to have superior soot dispersion and anti-wear properties. The main function of ashless dispersants is to prevent the aggregation of soot particles in diesel engine oil and avoid their sedimentation. Current research on lubricating oil dispersant systems suggests that the interaction between the dispersant and soot is the key factor determining the system's dispersion performance, and the size of the aggregated soot particles is directly related to the type and structure of the dispersant. Currently, the main methods for evaluating the dispersion performance of lubricating oils are simulation evaluation and bench testing. Bench testing methods are mainly divided into two categories: the American API method and the European CEC method. The API method includes Mack T-7, Mack T-8, Mack T-8A, Mack T-8E, and Mack T-11 bench tests, while the CEC method includes XUD11BET, DV4TD, and DV6 bench tests. These benches are used to evaluate the soot dispersion performance of lubricating oils and related viscosity growth.The aforementioned bench tests more closely resemble actual engine operating conditions, and their results can effectively evaluate the dispersion of soot by ashless dispersants. However, these bench tests often have long operating cycles, require significant fuel and equipment consumption, and are expensive, which is quite detrimental to the early development and selection of dispersants. Currently, there is an urgent need for a simple and efficient simulation evaluation method to quickly screen out optimized solutions in the initial stage of dispersant development, followed by further bench testing for verification. The main methods for evaluating the dispersion performance of engine soot in China include: sludge spot dispersion method, electron microscopy, particle size analyzer method, sedimentation method, and rotational rheological viscosity method. The sludge spot test method is mainly used to simulate the dispersion of low-temperature sludge and has a certain correlation with the sludge and varnish scores of gasoline engine oil VD and VE bench tests. However, it suffers from weak discrimination and poor repeatability in evaluating the dispersion ability of soot particles. The carbon black sedimentation test is used to study the dispersion stabilization effect of ashless dispersants and viscosity index improvers on soot. Carbon black is dissolved in base oil containing a dispersant, mechanically stirred to suspend it, and stored at 30°C for 169 hours. The concentration of residual carbon black in the supernatant is measured using visible light spectroscopy at 495 nm (the supernatant is diluted with white oil and compared with a standard carbon black solution). The difference in carbon black concentration before and after the test indicates the sedimentation of particulate matter and whether the additive effectively disperses and suspends the particulate matter. Viscosity is generally measured using the kinematic viscosity method (ASIM D445 or GB / T11237) with a countercurrent capillary viscometer. However, the countercurrent capillary viscosity method often produces deviations when used for viscosity determination of soot-containing oils. [Lubricating Oil, 2006(01)61-64] published a study on the simulation evaluation method of diesel engine oil dispersion performance. The authors used carbon black, which is similar to soot, as the test material. The carbon black was dispersed in the oil under high-speed stirring, and the dispersion performance of the oil was examined by the viscosity change. The study showed that this method can distinguish the same quality grade well, but it is difficult to distinguish the soot dispersion performance of diesel engine oils with different dispersion performance and soot dispersion performance of different dispersants. Patent CN102135507B discloses a method for simulating the dispersibility of engine oil. The method involves mixing test engine oil with 4% carbon black, stirring and heating to 90°C, and then using a mixture of 20% test engine oil and 80% n-pentane. Standard blotting paper is then brought into contact with this mixture in a 15 μL volume for 1 minute. The standard blotting paper is then placed in a 200 mm test tube containing 10 mL of the mixture, and the bottom of the blotting paper is immersed in the test tube until the carbon black is absorbed to the top. The results are then determined using an electron microscope, with 0 = all white and 100 = all areas are black. This method is highly operable, precise, and repeatable, and can serve as a prerequisite for screening engine lubricating oils.Patent CN102866227B evaluates the soot dispersibility in a lubricant formulation containing a dispersant through the following steps: (a) preparing a dispersion of carbon black in the lubricant formulation; (b) depositing a sample of dispersed carbon black from step (a) onto a planar chromatographic analysis medium; (c) subjecting the sample from (b) to chromatographic analysis conditions; and (d) evaluating the degree of carbon black migration by comparing the density of blackening caused by carbon black at a predetermined location along the chromatographic analysis medium. Patent CN105717282B discloses a method for testing the soot dispersion performance of engine oil. A test oil containing soot particles, obtained directly from a test bench, is added to engine oil and then placed in a rotational rheometer. The viscosity of the oil sample is measured over time under fixed shear rate and temperature conditions. The increase in viscosity and the slope are calculated for a specific time period, and the slope is measured. A smaller slope indicates better dispersibility of the engine oil. The viscosity measured by this method using a rotational rheometer is obtained under the condition of a certain soot content. The viscosity of different soot contents cannot be measured continuously. In addition, the test oil mentioned in this method contains other additives besides soot, and these other additives interfere with the viscosity index of the oil during the test.

[0003] As seen from the publicly available literature and patent reports, most oil samples currently used for simulating and evaluating the dispersion performance of lubricating oils employ carbon black to simulate soot. Carbon black particles are inorganic and differ significantly from real soot in structure and composition, resulting in a vastly different distribution in the oil. This leads to poor solubility and dispersibility, and a tendency to agglomerate and settle, which is the main reason for the lack of correspondence between simulation experiments and actual bench tests. Furthermore, current methods for simulating and evaluating the dispersion performance of lubricating oils are still quite limited, with many methods exhibiting poor repeatability and lacking a strong correlation and correspondence with bench tests and actual operating conditions, posing a significant obstacle to the early development of ashless dispersants. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a method for evaluating the dispersion performance of soot in lubricating oil. Firstly, the soot particles used are generated from the combustion of fuel oil in a soot generator, maximally replicating the soot generation process in the combustion chamber of an engine under operating conditions. The resulting soot is free of other lubricating oil additives, providing a raw material guarantee for subsequent evaluation of soot dispersion performance in lubricating oils. Secondly, this method employs a soot delivery system and an online kinematic viscosity measurement system to accurately and quantitatively input soot liquid into the reaction vessel. Then, a viscosity sensing probe is used to monitor the viscosity of the test oil online in real time, establishing a quantitative relationship between soot content and kinematic viscosity. The viscosity change directly reflects the dispersion of soot in the oil.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for evaluating the dispersion performance of lubricating oil soot, specifically comprising the following steps:

[0008] S1. Add the soot particles to the base oil and stir evenly to form a soot liquid;

[0009] S2. Add the lubricating oil to be tested into the reaction vessel equipped with a viscosity sensing probe and a gas delivery tube;

[0010] S3. Place the reactor in an oil bath, introduce air from the bottom of the reactor, and slowly add the soot liquid from step S1 to the reactor using a peristaltic pump. Turn on the viscometer to track and record the kinematic viscosity of the lubricating oil to be tested in step S2.

[0011] S4. When the kinematic viscosity of the lubricating oil to be tested increases to 200 mm... 2 When the time reaches 1 / s, the test is considered complete. Export the viscosity and corresponding time data from the viscometer and plot them. The flatter the curve in the graph, the better the dispersibility of the lubricating oil.

[0012] Preferably, the soot particles in step S1 are generated by the combustion of fuel oil in the soot generator and do not contain any other additive components.

[0013] Preferably, the concentration of the soot liquid in step S1 is 50-85%.

[0014] Preferably, the air flow rate in step S3 is 100-200 ml / min.

[0015] Preferably, the oil bath temperature in step S3 is 98-102℃.

[0016] Preferably, the flow rate of the peristaltic pump in step S3 is 0.5-0.9 g / h.

[0017] (3) Beneficial effects

[0018] This invention provides a method for evaluating the dispersion performance of lubricating oil soot. Compared with the prior art, it has the following advantages:

[0019] (1) The method for evaluating the dispersion performance of lubricating oil soot uses soot particles generated by the combustion of fuel oil in the soot generator, which maximizes the reproduction of the soot generation process in the combustion chamber of the engine under working conditions. The soot obtained is not mixed with other lubricating oil additive components, which provides a raw material guarantee for subsequent evaluation of the dispersion performance of soot in lubricating oil.

[0020] (2) The method for evaluating the dispersion performance of lubricating oil soot is to accurately and quantitatively input soot liquid into the reaction vessel by using a soot delivery system and an online kinematic viscosity measurement system, thereby simulating and restoring the dispersion of soot under the actual working conditions of the engine. Then, the viscosity of the test oil is monitored online in real time by using a viscosity sensing probe, and a quantitative relationship between soot content and kinematic viscosity is established. The dispersion of soot in the oil is reflected intuitively by the viscosity change. The test results of this method are consistent with the engine bench test results. Attached Figure Description

[0021] Figure 1 This is a flowchart of the evaluation method of the present invention;

[0022] Figure 2 This is a graph showing the relationship between soot or carbon black content and kinematic viscosity in Example 1 of the present invention.

[0023] Figure 3 This is a schematic diagram illustrating the effect of different dispersants on the oil dispersion performance in Example 2 of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] See also Figure 1-3 A method for evaluating the dispersion performance of lubricating oil soot includes the following steps:

[0026] S1. Add soot particles to base oil and stir evenly to form soot liquid with a concentration of 50-85%. The soot particles are produced by the combustion of fuel oil in the soot generator and do not contain other additive components.

[0027] S2. Add the lubricating oil to be tested into the reaction vessel equipped with a viscosity sensing probe and a gas delivery tube;

[0028] S3. Place the reaction vessel in an oil bath, introduce air from the bottom of the reaction vessel, and slowly add the soot liquid from step S1 to the reaction vessel using a peristaltic pump. Turn on the viscometer to track and record the kinematic viscosity of the lubricating oil to be tested in step S2. The air flow rate is 100-200 ml / min, the oil bath temperature is 98-102℃, and the peristaltic pump flow rate is 0.5-0.9 g / h.

[0029] S4. When the kinematic viscosity of the lubricating oil to be tested increases to 200 mm... 2When the time reaches 1 / s, the test is considered complete. Export the viscosity and corresponding time data from the viscometer and plot them. The flatter the curve in the graph, the better the dispersibility of the lubricating oil.

[0030] This invention provides two technical solutions:

[0031] Example 1: Comparative Test of Different Grades of Oil

[0032] Diesel engine oil grades are mainly based on two major systems: the American API (American Petroleum Institute) and the European ACEA (European Advanced Technology & Environment). Common API grades for diesel engine oils include CH, CI, CJ, and CK, with CK being the highest grade. Higher oil grades generally offer the best overall performance in terms of oxidation resistance, wear resistance, thermal stability, and the dispersibility of deposits such as soot.

[0033] In this embodiment, soot particles and carbon black particles were first added to base oil MVI150 to prepare soot and carbon black solutions with a concentration of 75%. Then, three commonly available grades of 15W-40 lubricating oil (CH-4, CI-4, CK-4) were selected as test oils. A total of six sets of experiments were designed (as shown in Table 1). Dispersion performance tests were conducted according to the above steps to track the kinematic viscosity of the oils under different soot contents. The recorded data were then plotted, and the results were analyzed as follows: Figure 2 As shown in the figure. The results show that when carbon black liquid is prepared using carbon black, the viscosity of the three test oils increases with the increase of carbon black content. When the carbon black content is around 3%, the viscosity of all three test oils increases sharply. Different grades of oils do not differentiate their dispersion performance, indicating that carbon black is difficult to disperse stably in the test oils. When the carbon black content reaches a certain value, it begins to agglomerate, causing the oil viscosity to increase. When soot liquid is prepared using soot, the viscosity of the three test oils increases slowly with the increase of soot content. The dispersion performance of different grades of oils in this case shows obvious differentiation, especially the CK-4 grade test oil, which has excellent soot dispersion performance, followed by CI-4, and CH-4 is the worst. Comparative experiments revealed that the soot produced after fuel oil combustion in the soot generator closely replicates the soot generation process in the combustion chamber of an engine under operating conditions. The resulting soot is closer to the soot produced under actual engine operating conditions. This soot is free of other lubricating oil additives, providing a raw material guarantee for subsequent evaluation of the soot's dispersion performance in lubricating oils.

[0034] Table 1. Experimental Design of Dispersion Performance of Three Different Grades of Lubricating Oil

[0035]

[0036] Example 2: Comparative test of oil products of the same grade blended with different dispersants

[0037] To verify the correspondence between the lubricating oil soot dispersion performance evaluation method described in this invention and the engine bench test, this embodiment selected three ashless dispersants with different structures and formulated them into CI-4 15W-30 test oils of the same grade for dispersion performance testing. Ashless dispersant 1 was a commercially available low-molecular-weight polyisobutylene succinimide type T151; ashless dispersant 2 was a commercially available high-molecular-weight polyisobutylene succinimide type T161; and ashless dispersant 3 was a self-made aromatic amine-modified ashless dispersant RHY168. The CI-4 15W-30 test oils formulated with the above three dispersants of the same grade were subjected to bench tests on a Mack T-8E engine. The results are shown in Table 2. A lower relative viscosity based on thermogravimetric analysis at 4.8% soot content indicates better dispersibility. The results show that only ashless dispersant 3 passed the bench test, indicating that the dispersion performance of ashless dispersant 3 was superior to that of ashless dispersants 1 and 2, while the dispersion performance of ashless dispersant 1 was the worst.

[0038] Table 2. Bench test results of Mack T-8E engine for three types of CI-4 15W-40 test oils formulated with ashless dispersants.

[0039]

[0040] The three dispersants described above were used to prepare CI-4 15W-30 test oils of the same grade, B1, B2, and B3. Dispersion performance tests were conducted according to the above methods and procedures, tracking the kinematic viscosity of the oils under different soot contents. The recorded data were then plotted, and the results were analyzed as follows: Figure 3 As shown in the figure, the results indicate that as the soot content in the test oil increases, the kinematic viscosity of B1, B2, and B3 initially increases slowly. When the soot content exceeds 4%, the kinematic viscosity of B1 begins to increase rapidly, while B2 increases more slowly, and B3 increases at the slowest rate. This suggests that ashless dispersant 3 (RHY168) has good dispersibility for soot, while ashless dispersants 1 and 2 have relatively poor dispersibility. These experimental results are consistent with the bench test results of the Mack T-8E engine. This method can effectively distinguish and screen dispersants with different structures, providing a rapid and effective detection method for the early development of ashless dispersants.

[0041] In summary, this invention utilizes soot particles generated from the combustion of fuel oil in a soot generator, maximally replicating the soot generation process in the combustion chamber of an engine under operating conditions. The resulting soot is free of other lubricating oil additives, providing a raw material guarantee for subsequent evaluation of soot dispersion performance in lubricating oils. Furthermore, by employing a soot delivery system and an online kinematic viscosity measurement system, soot liquid is accurately and quantitatively introduced into the reaction vessel, simulating and recreating the soot dispersion under actual engine operating conditions. Then, a viscosity sensing probe is used to monitor the viscosity of the test oil in real time, establishing a quantitative relationship between soot content and kinematic viscosity. Viscosity changes directly reflect the soot dispersion in the oil, and the test results obtained by this method are consistent with those of engine bench tests.

[0042] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0043] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0044] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for evaluating the dispersion performance of lubricating oil soot, characterized in that: Specifically, the following steps are included: S1. Add the soot particles to the base oil and stir evenly to form a soot liquid; S2. Add the lubricating oil to be tested into the reaction vessel equipped with a viscosity sensing probe and a gas delivery tube; S3. Place the reactor in an oil bath, introduce air from the bottom of the reactor, and slowly add the soot liquid from step S1 to the reactor using a peristaltic pump. Turn on the viscometer to track and record the kinematic viscosity of the lubricating oil to be tested in step S2. S4. When the kinematic viscosity of the lubricating oil to be tested increases to 200 mm... 2 When the time reaches / s, the test is considered to be over, and the viscosity and corresponding time data in the viscometer are exported and plotted. The soot particles in step S1 are produced by the combustion of fuel oil in the soot generator and do not contain any other additive components. The air flow rate in step S3 is 100-200 ml / min; The oil bath temperature in step S3 is 98-102℃; In step S3, the flow rate of the peristaltic pump is 0.5-0.9 g / h; The concentration of the soot liquid in step S1 is 50-85%.

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