Evaluation method for engine oil soot dispersibility and dispersion stability

Abstract

The present invention relates to the technical field of engine oil performance evaluation, and specifically to a method for evaluating the soot dispersion ability and dispersion stability of engine oil. The method comprises the following steps: uniformly stirring the engine oil to be tested and carbon black to obtain a mixed sample; the difference between the measured value of the kinematic viscosity of the mixed sample when the kinematic viscosity reaches stability and the measured value of the kinematic viscosity of the engine oil to be tested is defined as the kinematic viscosity increase value, and the smaller the kinematic viscosity increase value, the better the soot dispersion ability of the engine oil; the static treatment time when the kinematic viscosity reaches stability is the dispersion stability time, and the shorter the dispersion stability time, the better the soot dispersion stability of the engine oil. The test materials used in the evaluation method are generally available, the test steps are simple and easy to operate, and the test results can simultaneously reflect the two indicators of the soot dispersion ability and dispersion stability of the engine oil, and can comprehensively examine the impact of soot on the engine oil.

Description

Technical Field

[0001] The invention relates to the technical field of engine oil performance evaluation, and in particular to a method for evaluating the soot dispersibility and dispersion stability of engine oil. Background Art

[0002] As environmental protection regulations have increasingly stringent requirements on automobile engine emissions, engine manufacturers have adopted a series of new engine technologies such as turbochargers, engine delayed injection technology, and exhaust gas recirculation to meet emission regulations. These technologies have greatly improved engine emissions, but at the same time, they have also caused the engine to produce more soot during operation. Modern engine oils, especially diesel engine oils, need to accommodate a large amount of soot generated by combustion during use. These soots are dispersed in the engine oil through the dispersing additives in the engine oil and will not aggregate and precipitate. Different engine oil additive formulas have different soot dispersing abilities, which are mainly manifested in the different amounts of dispersed soot and the different stability of the dispersion system.

[0003] The American Petroleum Institute (API) has specified more stringent engine tests in engine specifications of all levels to evaluate the oil's dispersion performance on soot. For example, in a series of oil specifications from CF-4 to CJ-4, engine test procedures such as Mack T-8A, Mack T-8, Mack T-8E, Mack T-8E+, and Mack T-11 are used to evaluate the oil's ability to inhibit viscosity growth caused by soot. The European Automobile Manufacturers Association (ACEA) also specifies a more stringent engine bench test CEC L-093-04 (DV4TD) to evaluate viscosity growth caused by soot. The above-mentioned engine bench tests used to evaluate viscosity growth caused by soot are very expensive and take a long time to test. Therefore, simulation tests are essential in the process of formula development. Simulation tests with good correlation with bench tests can greatly save test cycles and costs, and achieve twice the result with half the effort.

[0004] The Chinese invention patent discloses a method for simulating the dispersibility of engine oil with the application number 201010605038.3. The test oil is mixed with 4% carbon black, stirred and heated to 90°C, and a mixture of 20% test oil and 80% n-pentane is used to form a mixture, and a standard blotting paper is contacted with it, with a contact volume of 15μL, and adsorbed for 1min; the standard blotting paper is placed in a 200mm test tube, and the test tube is filled with 10mL of the above-mentioned mixture, and the bottom of the standard blotting paper is immersed in the test tube until the carbon black is absorbed to the top of the standard blotting paper; the judgment is made by scanning with an electron microscope. The Chinese invention patent discloses a method for testing the dispersibility of engine oil soot with the application number 201410738790.3. Add soot particles to engine oil and stir to mix evenly to form an oil sample to be tested; place the oil sample to be tested in a rotational rheometer and measure the viscosity of the oil sample over time under fixed shear rate and fixed temperature conditions; calculate the viscosity increase value and slope in a certain period of time, and measure the slope. The smaller the slope, the better the dispersibility of the engine oil. The above inventions fail to examine the dispersibility and dispersion stability of the engine oil at the same time.

[0005] Therefore, it is very important for oil product development to establish a simulation test method that can examine both the amount of soot dispersed by engine oil and the stability of the dispersion system. Summary of the invention

[0006] The inventors of the present invention have fully considered the characteristics of the soot dispersing ability of engine oil and provided an evaluation method for the soot dispersing ability and dispersion stability of engine oil, which can conduct investigations on the two indicators of the soot dispersing ability and dispersion stability of engine oil.

[0007] Specifically, the present invention provides the following technical solutions:

[0008] A method for evaluating the dispersibility and dispersion stability of engine soot comprises the following steps:

[0009] The engine oil to be tested and the carbon black are stirred uniformly at a first temperature below the flash point temperature of the engine oil to be tested to obtain a mixed sample;

[0010] Then, the mixed sample is allowed to stand at the first temperature;

[0011] Detecting the kinematic viscosity of the engine oil to be tested and the kinematic viscosity of the statically treated mixed sample;

[0012] The difference between the measured value of the kinematic viscosity of the mixed sample after the static treatment when it reaches stability and the measured value of the kinematic viscosity of the engine oil to be tested is defined as the kinematic viscosity increase value, and the smaller the kinematic viscosity increase value is, the better the soot dispersibility of the engine oil at the first temperature is;

[0013] The static treatment time when the kinematic viscosity of the mixed sample after the static treatment reaches stability is the dispersion stabilization time. The shorter the dispersion stabilization time is, the better the soot dispersion stability of the engine oil at the first temperature is.

[0014] Preferably, in the above-mentioned evaluation method for the soot dispersibility and dispersion stability of engine oil, the mass ratio of the carbon black to the engine oil to be tested is 0.01 to 5:100.

[0015] Preferably, in the above-mentioned evaluation method for the soot dispersibility and dispersion stability of engine oil, the mass ratio of the carbon black to the engine oil to be tested is 0.5 to 1:100.

[0016] Preferably, in the above-mentioned evaluation method for the engine soot dispersibility and dispersion stability, the particle size of the carbon black is 5 to 200 nm.

[0017] Preferably, in the above-mentioned evaluation method for the engine soot dispersibility and dispersion stability, the particle size of the carbon black is 20 to 100 nm.

[0018] Preferably, in the above-mentioned evaluation method for the dispersibility and dispersion stability of engine soot, the stirring speed is 3000-30000 rpm, and the stirring time is not less than 5 minutes.

[0019] Preferably, in the above-mentioned evaluation method for the dispersibility and dispersion stability of engine soot, the stirring speed is 15000-25000 rpm.

[0020] Preferably, in the above-mentioned evaluation method for the engine oil soot dispersibility and dispersion stability, the first temperature is room temperature to 50° C. below the flash point temperature of the engine oil to be tested.

[0021] Preferably, in the above-mentioned evaluation method of engine oil soot dispersibility and dispersion stability, the kinematic viscosity of the engine oil to be tested and the kinematic viscosity of the statically treated mixed sample are detected at a second temperature of not less than 40° C. and not more than 150° C.

[0022] The beneficial effects of the present invention are:

[0023] The present invention provides an evaluation method for the soot dispersibility and dispersion stability of engine oil. The test materials used are generally available, the test steps are simple and easy to operate, and the test results can simultaneously evaluate the soot dispersibility and dispersion stability of the engine oil, and can comprehensively examine and compare the advantages and disadvantages of the soot dispersibility of different engine oils. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with specific embodiments, but is not intended to limit the scope of the present invention.

[0025] The experimental methods used in the following examples are conventional methods unless otherwise specified. The experimental raw materials and related equipment used in the following examples are all commercially available unless otherwise specified.

[0026] Example 1 Investigation of the soot dispersibility of a diesel engine oil

[0027] 1% carbon black with a particle diameter of 50nm was added to the Great Wall Dragon T500 15W-40 diesel engine oil, and stirred at 20,000rpm with a high-speed stirrer at room temperature 25℃ for 10 minutes. The mixed sample was left to stand at room temperature 25℃. The kinematic viscosity of the Great Wall Dragon T500 15W-40 diesel engine oil and the kinematic viscosity of the statically treated mixed sample were tested (capillary viscometer). The statically treated mixed sample was extracted from the sample surface by a sampler, and the temperature for testing the kinematic viscosity was 40℃.

[0028] The kinematic viscosity values ​​at different standing treatment times were tested. When the kinematic viscosity value remained unchanged, it meant that the kinematic viscosity reached stability. The kinematic viscosity measured value of the Great Wall Dragon T500 15W-40 diesel engine oil was subtracted from the measured value of the kinematic viscosity of the standing mixed sample when the kinematic viscosity reached stability to obtain the kinematic viscosity increase value. The kinematic viscosity increase value reflects the dispersion ability of the Great Wall Dragon T500 15W-40 diesel engine oil on soot of the corresponding particle diameter at 25°C. The standing treatment time when the kinematic viscosity of the standing mixed sample reached stability was taken as the dispersion stability time, and the dispersion stability time reflects the soot dispersion stability of the Great Wall Dragon T500 15W-40 diesel engine oil at 25°C.

[0029] The specific test results are:

[0030] Great Wall Zunlong T500 15W-40 diesel engine oil 40℃ kinematic viscosity 110.8mm 2 / s;

[0031] After the mixed sample was left to stand for 30 minutes, the kinematic viscosity at 40°C was 130.5 mm 2 / s;

[0032] After the mixed sample was left to stand for 40 minutes, the kinematic viscosity at 40°C was 120.5 mm 2 / s;

[0033] After the mixed sample was left to stand for 45 minutes, the kinematic viscosity at 40°C was 119.3 mm 2 / s;

[0034] After the mixed sample was left to stand for 50 minutes, the kinematic viscosity at 40°C was 119.3 mm 2 / s.

[0035] It can be seen that at room temperature of 25°C, the kinematic viscosity increase of Great Wall Zunlong T500 15W-40 diesel engine oil at 40°C is 8.5mm 2 / s, and the dispersion stabilization time is 45min.

[0036] Example 2

[0037] The soot dispersibility of Shell Rimula R4 X 15W-40 diesel engine oil was investigated by the same method as in Example 1. The results showed that at room temperature of 25°C, the increase in the kinematic viscosity of the engine oil at 40°C was 10.2 mm 2 / s, and the dispersion stabilization time is 55min.

[0038] By comparing the results with those of Example 1, it can be seen that compared with Shell Rimula R4 X 15W-40 diesel engine oil, Great Wall Zunlong T500 15W-40 diesel engine oil has better soot dispersion ability and soot dispersion stability.

[0039] Example 3 Investigation of the dispersibility of gasoline engine oil soot

[0040] Mobil 1 SN 5W-30 gasoline engine oil was added with 0.5% carbon black with a particle diameter of 100nm, and stirred at 100℃ for 15min with a high-speed stirrer at a speed of 15000rpm. The mixed sample was left to stand at 100℃. The kinematic viscosity of Mobil 1 SN 5W-30 gasoline engine oil and the kinematic viscosity of the statically treated mixed sample were tested (capillary viscometer). The statically treated mixed sample was extracted on the sample surface by a sampler, and the temperature for testing the kinematic viscosity was 100℃.

[0041] The kinematic viscosity values ​​at different standing treatment times are detected. When the kinematic viscosity value remains unchanged, it means that the kinematic viscosity has reached stability. The kinematic viscosity measured value of Mobil 1 SN 5W-30 gasoline engine oil is subtracted from the kinematic viscosity measured value of the standing mixed sample when the kinematic viscosity reaches stability to obtain the kinematic viscosity increase value. The kinematic viscosity increase value reflects the dispersion ability of Mobil 1 SN 5W-30 gasoline engine oil for soot of corresponding particle diameter at 100°C. The standing treatment time when the kinematic viscosity of the standing mixed sample reaches stability is taken as the dispersion stability time, and the dispersion stability time reflects the soot dispersion stability of Mobil 1 SN 5W-30 gasoline engine oil at 100°C.

[0042] The specific test results are:

[0043] Mobil 1 SN 5W-30 gasoline engine oil 100℃ kinematic viscosity 10.2mm 2 / s

[0044] After the mixed sample was left to stand for 30 minutes, the kinematic viscosity at 100°C was 13.5 mm2 / s

[0045] After the mixed sample was left to stand for 40 minutes, the kinematic viscosity at 100°C was 12.2 mm 2 / s

[0046] After the mixed sample was left to stand for 45 minutes, the kinematic viscosity at 100°C was 11.9 mm 2 / s

[0047] After the mixed sample was left to stand for 50 minutes, the kinematic viscosity at 100°C was 11.6 mm 2 / s

[0048] After the mixed sample was left to stand for 55 minutes, the kinematic viscosity at 100°C was 11.6 mm 2 / s

[0049] It can be seen that at 100°C, the kinematic viscosity increase of Mobil 1 SN 5W-30 gasoline engine oil at 100°C is 1.4 mm 2 / s, and the dispersion stabilization time is 50min.

[0050] Example 4

[0051] The soot dispersibility of Castrol Magnetron SN 5W-30 gasoline engine oil was investigated by the same method as in Example 3. The results showed that at 100°C, the increase in kinematic viscosity of the engine oil at 100°C was 0.9 mm 2 / s, and the dispersion stabilization time is 45min.

[0052] By comparing the results with those of Example 3, it can be seen that Castrol Magnetic SN 5W-30 gasoline engine oil has better soot dispersibility and soot dispersion stability than Mobil 1 SN 5W-30 gasoline engine oil.

[0053] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for evaluating the dispersibility and dispersion stability of engine soot, characterized in that: The following steps are involved: The engine oil to be tested and the carbon black are stirred uniformly at a first temperature below the flash point temperature of the engine oil to be tested to obtain a mixed sample; Then, the mixed sample is allowed to stand at the first temperature; Detecting the kinematic viscosity of the engine oil to be tested and the kinematic viscosity of the statically treated mixed sample; The difference between the measured value of the kinematic viscosity of the mixed sample after the static treatment when it reaches stability and the measured value of the kinematic viscosity of the engine oil to be tested is defined as the kinematic viscosity increase value, and the smaller the kinematic viscosity increase value is, the better the soot dispersibility of the engine oil at the first temperature is; The static treatment time when the kinematic viscosity of the mixed sample after the static treatment reaches stability is the dispersion stabilization time. The shorter the dispersion stabilization time is, the better the soot dispersion stability of the engine oil at the first temperature is.

2. The method for evaluating the engine soot dispersibility and dispersion stability according to claim 1, characterized in that: The mass ratio of the carbon black to the engine oil to be tested is 0.01 to 5:

100.

3. The method for evaluating the engine soot dispersibility and dispersion stability according to claim 2, characterized in that: The mass ratio of the carbon black to the engine oil to be tested is 0.5 to 1:

100.

4. The method for evaluating the engine soot dispersibility and dispersion stability according to any one of claims 1 to 3, characterized in that: The particle size of the carbon black is 5 to 200 nm.

5. The method for evaluating the engine soot dispersibility and dispersion stability according to claim 4, characterized in that: The particle size of the carbon black is 20 to 100 nm.

6. The method for evaluating the engine soot dispersibility and dispersion stability according to any one of claims 1, 2, 3 and 5, characterized in that: The stirring speed is 3000-30000 rpm, and the stirring time is not less than 5 minutes.

7. The method for evaluating the engine soot dispersibility and dispersion stability according to claim 6, characterized in that: The stirring speed is 15000-25000 rpm.

8. The method for evaluating the engine soot dispersibility and dispersion stability according to any one of claims 1, 2, 3 and 5, characterized in that: The first temperature is from room temperature to 50° C. below the flash point temperature of the engine oil to be tested.

9. The method for evaluating the engine soot dispersibility and dispersion stability according to any one of claims 1, 2, 3 and 5, characterized in that: The kinematic viscosity of the engine oil to be tested and the kinematic viscosity of the mixed sample subjected to the static treatment are detected at a second temperature of not less than 40° C. and not more than 150° C.