RU2695704C1 - Forecasting method of thermo-oxidative stability of lubricant materials - Google Patents

Abstract

FIELD: measurement technology.

SUBSTANCE: invention relates to technology of determining indicators of thermal oxidative stability of lubricants. To achieve technical result, disclosed is a method for predicting values of thermal oxidative stability of lubricants, in which a heated lubricant sample is tested in the presence of air with mixing constant weight for a period of time, and at regular intervals of time an oxidised lubricant sample is sampled and an oxidation process is evaluated. According to the invention, in order to predict the values of thermal oxidative stability while increasing the time for testing the lubricant at the selected temperature, using the results obtained at least three identical time intervals, calculating the amount of heat energy absorbed by the oxidation products, the evaporation products, and total absorbed heat energy during the lubricant temperature control, the amount of heat energy is determined by the product of the temperature value for the test time and the value of the thermo-oxidative stability value, calculating logarithm of absorbed heat energy by each indicator of thermal-oxidative stability for at least three selected intervals of test time, plotting graphical dependencies of decimal logarithm of absorbed heat energy by each indicator of thermal-oxidative stability on decimal logarithm of test time, on which values of optical density, volatility and thermal oxidative stability coefficient are predicted with increase in test time interval.

EFFECT: technical result consists in reduction of labor intensity due to reduced time of testing at selected temperature in connection with possibility to use results obtained at three identical time intervals, and possibility of forecasting with obtaining of values of parameters by calculation method.

1 cl, 3 dwg, 1 tbl

Description

The invention relates to a technology for determining the thermal oxidative stability of lubricants.

A known method for determining the thermo-oxidative stability of lubricants, including heating the lubricant in the presence of air, mixing, photometry and determining the parameters of the oxidation process (RF Patent No. 22199530 C1, priority date 04/11/2002, publication date 12/20/2003, authors Kovalsky BI and other, RU).

The closest in technical essence and the achieved result is a method of predicting the thermal oxidative stability of lubricants adopted as a prototype, in which a lubricant sample is tested in the presence of air with constant weight mixing at a minimum of three temperatures, selected depending on the base base, purpose and operating group properties over a period of time characterizing the same degree of oxidation, and at regular intervals I select t of a sample of oxidized lubricant and evaluate the oxidation process, and to assess the oxidation process, determine the optical density, volatility and coefficient of thermo-oxidative stability, build a graphical dependence of these indicators on time and three selected test temperatures, determine the time to reach the selected values of thermo-oxidative stability from minimum to the maximum value at each temperature, determine the decimal logarithm of the time to reach the selected values renders of thermal oxidative stability, build graphical dependences of the decimal logarithm of the time to reach the selected values of the indicators of thermal oxidative stability on the test temperature, and forecasting the values of these indicators at other temperatures other than accepted, carry out the values of the antilogarithms of the time to reach the indicators of thermal oxidative stability for these temperatures (RF Patent No. 2649660 , priority date 05/03/2017, publication date 04/04/2018, authors Kovalsky B.I. et al., RU, prototype).

A common disadvantage of the analogue and prototype is the inability to predict the values of thermal oxidative stability, including optical density, volatility and coefficient of thermal oxidative stability depending on the test time for any temperature.

The technical problem solved by the invention is the creation of a method for predicting the values of thermal oxidative stability of lubricants depending on the test time based on data obtained at least three times for a selected temperature.

To solve this problem, a method for predicting the thermal oxidative stability of lubricants is proposed, in which a heated sample of a lubricant is tested in the presence of air with constant mass mixing over time, and an oxidized lubricant sample is taken at regular intervals and an oxidation process is evaluated. According to the invention, to predict the values of thermo-oxidative stability with an increase in the test time of the lubricant at the selected temperature, the results obtained at least at three identical time intervals are used, the amount of thermal energy absorbed by the oxidation products, evaporation products and the total absorbed thermal energy during thermostatting of the lubricant are calculated, the amount of thermal energy is determined by the product of the temperature value during the test and the value of the indicator of thermal oxidative stability, calculate the decimal logarithm of the absorbed thermal energy by each indicator of thermal oxidative stability for at least three selected intervals of the test time, build the graphical dependence of the decimal logarithm of the absorbed thermal energy by each indicator of thermal oxidative stability on the decimal logarithm of the test time, which predict the values of optical density, volatility and coefficient of thermo-oxidative stability with uve increasing the time interval of the test.

As an example, a method for predicting thermal oxidative stability is given, which involves testing a partially synthetic Total Quartz 10W-40 SL / CF engine oil at four temperatures: 190 ° C, 180 ° C, 170 ° C, and 160 ° C, and determining the optical density D, volatility G and coefficient of thermo-oxidative stability P _TOC , and at temperatures of 190 and 180 ° C, tests were carried out to a value of optical density equal to 0.5-0.6 units, and at temperatures of 170 and 160 ° C, tests were carried out for 30 hours and after each 10 hours test about Biranne oxidized oil samples to determine the optical density and the coefficient of evaporation thermooxidative stability. Then, according to the obtained data, a calculation was made of the prediction of thermal oxidative stability after 10 hours to 90 hours of testing for a temperature of 170 ° C and up to 140 hours for a temperature of 160 ° C. In addition, tests of samples at temperatures of 170 ° C and 160 ° C continued for a specified time (90 and 140 hours) to verify the convergence of experimental and calculation methods for determining the indicators of thermo-oxidative stability.

In FIG. Figure 1 shows the dependences of the decimal logarithm of the thermal energy absorbed by the oxidation products on the decimal logarithm of the time and temperature of the test of the partially synthetic Total Quartz 10W-40 SL / CF motor oil: 1 - 190 ° C; 2 - 180 ° C; 3 - 170 ° C; 4 - 160 ° C.

In FIG. 2 - dependences of the decimal logarithm of the thermal energy absorbed by the evaporation products on the decimal logarithm of the time and temperature of the test of the partially synthetic Total Quartz 10W-40 SL / CF motor oil: 1 - 190 ° C; 2 - 180 ° C; 3 - 170 ° C; 4 - 160 ° C.

In FIG. 3 - dependences of the decimal logarithm of the total thermal energy absorbed by the products of oxidation and evaporation, characterizing the coefficient of thermo-oxidative stability, on the decimal logarithm of the time and temperature of the test of partially synthetic engine oil Total Quartz 10W-40 SL / CF: 1 - 190 ° C; 2 - 180 ° C; 3 - 170 ° C; 4 - 160 ° C.

To obtain these graphical dependencies and the implementation of the method, it is necessary to obtain data on optical density, volatility and coefficient of thermo-oxidative stability. For this purpose, samples of constant weight lubricant are thermostated at selected temperatures with mixing by a mechanical stirrer with a constant speed. At regular intervals, for example 10 hours, the sample of oxidized lubricant is weighed, the mass of evaporated oil m is determined and the coefficient of evaporation K _{G is} calculated

where m is the mass of the evaporated lubricant during the oxidation time (10 hours), g; M is the mass of the sample of lubricant before the test,

A portion of the oxidized sample is taken for photometry and determination of the optical density D

where 300 is the photometer reading with an empty cell, µA; P - photometer readings when the cell is filled with oxidized oil, μA.

According to the data of D and K _{G, the} coefficient of thermo-oxidative stability P _{TOS was} calculated

During thermostating of lubricants, part of the thermal energy is absorbed by the oxidation products, changing the optical density, and part by the evaporation products, changing the mass of the evaporated lubricant, therefore, it is proposed to determine the amount of thermal energy Q absorbed by the products of oxidation and evaporation:

- for optical density

where T is the temperature control temperature, ° C; t is the test time, h; D is the optical density over time t, units;

- for evaporation

where G is the volatility of the oil, g;

- for coefficient of thermo-oxidative stability

(фиг. 3).The results of the test and calculation of the indicators of thermal oxidative stability are summarized in the table and are presented by the dependences: logQ _D = ƒ (logt, T) (Fig. 1); logQ _G = ƒ (logt, T) (Fig. 2) and

(Fig. 3).

In FIG. Figure 1 shows the dependences of the decimal logarithm of the thermal energy absorbed by the oxidation products on the decimal logarithm of the time and test temperature of the test engine oil. At a temperature of 190 ° C (curve 1), the oil was tested for 40 hours, and at a temperature of 180 ° C - 60 hours (curve 2). These dependences are described by linear equations for temperatures:

For temperatures of 170 ° C (curve 3) and 160 ° C (curve 4), the test oil was tested at the beginning of 30 hours, while the analysis was performed after 10 hours. Based on the results of three values of the decimal logarithm of the thermal energy absorbed by the oxidation products, graphical dependences on the decimal logarithm of time are constructed, which are described by linear equations for temperatures:

According to formulas 9 and 10, the logQ _D values were calculated for the test oil test time at a temperature of 170 ° C up to 90 hours of testing (logt = 1,954) and temperatures of 160 ° C up to 140 hours (logt = 2,146) with an increase of time by 10 hours and sampling oils for analysis.

For example, at a temperature of 160 ° C, it is necessary to determine the value of optical density during a test of 50 hours (log = 1.7) using the formula (10) or FIG. 1. First, the decimal logarithm of the thermal energy absorbed by the oxidation products is determined

since Q _D = T⋅t⋅D and the antilogarithm of 2.673 is 470.98, and since 470.98 = T⋅t⋅D = 160⋅50⋅D, D = 470.98 / 8000 = 0.059 units.

Comparing with experimental data (see table), at a test time of 50 hours, the optical density was 0.06. The relative error was 1.66%.

Further tests of the test oil at temperatures of 170 and 160 ° C showed that the experimental data fell on lines 3 and 4.

The dependences of the decimal logarithm of the thermal energy absorbed by the products of evaporation (Fig. 2) on the decimal logarithm of the test time are constructed in a similar way. These dependences are described by linear equations for temperatures:

Using formulas 14 and 15, the values of logQ _{G were} calculated for the test time of the test oil at temperatures of 170 and 160 ° C. For example, at a temperature of 160 ° C it is necessary to determine the value of volatility during a test of 50 hours (log = 1.7) using the formula (15) or FIG. 2. The decimal logarithm of the thermal energy absorbed by the evaporation products is determined

since Q _G = T⋅t⋅G = 4.2545, and the antilogarithm of 4.2545 is 17968, and since 17968 = T⋅t⋅G = 160⋅50⋅G, G = 17968/8000 = 2.246 g.

Comparing with experimental data (see table), at a test time of 50 hours, volatility was 2.2316 g. The relative error was 0.64%.

The dependences of the decimal logarithm of the total thermal energy absorbed by the products of oxidation and evaporation on the decimal logarithm of the test time are constructed in the same way (Fig. 3). These dependences are described by linear equations for temperatures:

для времени испытания исследуемого масла при температурах 170 и 160°С. Например, при температуре 160°С необходимо определить значение коэффициента термоокислительной стабильности П_ТОС за время испытания 50 часов (lgt=1,7) используя формулу (20) или фиг. 3, определяется десятичный логарифм суммарной тепловой энергии, поглощенной продуктами окислении и испаренияFormulas 19 and 20 calculated the values

for the test time of the test oil at temperatures of 170 and 160 ° C. For example, at a temperature of 160 ° C, it is necessary to determine the value of the coefficient of thermo-oxidative stability P _TOC for the test time of 50 hours (logt = 1.7) using the formula (20) or FIG. 3, the decimal logarithm of the total thermal energy absorbed by the products of oxidation and evaporation is determined

и антилогарифм 2,85 составляет 707,95, а так как 707,95=T⋅t⋅П_ТОС=160⋅50⋅П_ТОС, то П_ТОС=707,95/8000=0,0885 ед.because

and the antilogarithm of 2.85 is 707.95, and since 707.95 = T⋅t⋅P _TOC = 160⋅50⋅P _TOC , then P _TOC = 707.95 / 8000 = 0.0885 units.

Comparing the calculated data of the coefficient of thermo-oxidative stability P _TOC = 0.0885 units with experimental (see table) P _TOC = 0.0927 units, it was found that the relative error was 4.5%.

Using equations 7-20, it is possible to predict the values of the indices of thermo-oxidative stability D, G and P _TOC for any test time, using the dependences obtained for three ranges of test time.

Thus, the proposed technical solution allows to reduce the complexity of determining indicators of thermo-oxidative stability in a wide time interval by more than two times and is industrially applicable.

Moreover, the technical result achieved by implementing the method for predicting the indicators of thermo-oxidative stability of lubricants is to reduce the complexity by reducing the test time at the selected temperature in connection with the possibility of using the results obtained at three identical time intervals, and the possibility of forecasting to obtain the calculated values method.

A method for predicting the thermal oxidative stability of lubricants

Claims (1)

A method for predicting the thermal oxidative stability of lubricants, in which a heated sample of a lubricant is tested in the presence of air with constant mass stirring over time, and an oxidized lubricant sample is taken at regular intervals and an oxidation process is evaluated, characterized in that for predicting the values of the indicators thermal oxidative stability with increasing test time of the lubricant at a selected temperature using re the results obtained for at least three identical time intervals calculate the amount of thermal energy absorbed by the oxidation products, evaporation products and the total absorbed thermal energy during thermostatting of the lubricant, the amount of thermal energy is determined by the product of the temperature by the test time and the value of the thermal oxidative stability index, and the decimal logarithm is calculated thermal energy absorbed by each indicator of thermal oxidative stability for at least three the selected test time intervals, graphical dependencies of the decimal logarithm of the absorbed thermal energy by each thermo-oxidative stability index on the decimal logarithm of the test time are built, which predict the value of optical density, volatility and coefficient of thermo-oxidative stability with increasing test time interval.

Images