Determination of antioxidant content in aircraft kerosene

FIELD: engines and pumps.

SUBSTANCE: proposed method consists in application of the dependence of kerosene compatibility with rubber upon content of antioxidant therein for determination of antioxidant amount in tested kerosene. Rubber seal ring is used as the rubber specimen in proposed method. Said ring is compressed to 20% of its thickness, placed in tested kerosene to fix compression force continuously during the entire test for determination of compatibility of kerosene with rubber. Compatibility index is calculated by the formula including maximum rubber ring compression force and ring compression force after 3 hours of holding said ring in kerosene at 150°C.

EFFECT: perfected method.

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The invention relates to a method of evaluating performance characteristics of fuels for aircraft gas turbine engines (jet fuel), in particular, to determine the content of antioxidants and can be used in petrochemical, aviation and other industries.

Straight-run jet fuel, such as TS-1, contain natural antioxidants. In the formulation of thermostable jet fuel RT, T-6 and other straight-run component is subjected to hydrogenation and injected into him antioxidant Agidol(2,6-di-tertbutyl-4-METHYLPHENOL) in an amount of 0.003-0,004% wt. with the known effectiveness of inhibition. In mixed jet fuel TS-1 is the decrease in the content of natural antioxidants in the dilution straight unstabilized component of the hydrogenation product in an amount up to 70% (vol.).

Natural antioxidants in virgin jet fuel and Agidol introduced at the plant in the amount of 0.003-0,004% (wt.) in hydrogenated jet fuel (according to documentation) so as to prevent destruction of rubber products (rubber) fuel systems for gas turbine engines (hereinafter CCD), as well as to carry out long-term storage of jet fuel.

During long-term storage, the content of antioxidants in the jet fuel is reduced (as a result of their interaction with free radicals) meant to the th significantly lower than 0,003% (wt.), and the quality of jet fuel for some time can be satisfactory, so you can use them on purpose. This implies the necessity of control over the content of antioxidants in the jet fuel, which will increase the reliability of aircraft operation.

Known methods of chemical, spectral, poligraficheskogo determine the amount of antioxidants in jet fuel (JET Denisov, Kovalev GI. "Oxidation and stabilization of jet fuels), Izd-vo "Chemistry", 1983, p.137). Using these methods, you can determine the number of Agidol concentration should be below 0.01% (wt.), that is unacceptable for jet fuel, because the content of Agidol is 0,003-0,004% (wt.).

There is a method of quantitative determination of Agidol hydrogenated in the jet fuel with acceptable sensitivity of 0.0005% (wt.). The method consists in the oxidation of the sample hydrogenated kerosene without Agidol and samples with different content of Agidol oxygen at 120°C in the presence of initiator oxidation with subsequent measurement of the induction periods for the accumulation of hydroperoxides and applying the values of the induction period of the test jet fuel on the calibration graph constructed in the coordinates of the induction period, the concentration of antioxidants (AS the USSR is the 648905, G01 N 31/00). With acceptable sensitivity Agidol can also be defined in the hydrogenated jet fuel chrome-mass spectrometry.

The main disadvantage of these methods is the inability to determine the number of natural antioxidants in virgin jet fuel. As straight-run jet fuel contain antioxidants in the form of a variety of compounds of different composition, their overall effectiveness can only be assessed through indirect indicators, such as indicator of the compatibility of jet fuel with rubber, used in aircraft turbine engines.

The number of known ways of assessing the compatibility of jet fuel with rubber (A.A. Gureev and other "Qualification, test methods for petroleum fuels), Izd-vo "Chemistry", 1984, p.148).

Closest to the claimed method and used as a prototype is a method of assessing the compatibility of jet fuel with rubber, on which a sealing ring of rubber used in the fuel systems of gas-turbine engine from which previously removed antioxidants, placed in a device for compression of the sealing ring (20% of its thickness), which is then put in an airtight container with the test jet fuel, Then the container is placed in a thermostat heated to 150°C and stabilized at this temperature. The compressing force F1using the sensor measurement efforts to continuously contact aliroot throughout the test and get the dependence of Fj from time τ, then based on this finding the maximum compressing force F1and through τ=4 hours after fixation F1at the same dependencies define the compressing force F2and calculate the value of WI.compatibility tested with jet fuel rubber (Patent No. 2475738, G01 N 33/22).

The disadvantage of this method is the inability to determine the number of antioxidants in the test jet fuel.

The technical result of the invention: expanding the range of controllable parameters of jet fuel without reducing the accuracy requirements determine the compatibility of the test jet fuel with rubber, as well as the application to determine the amount of antioxidants found in jet fuel, the resulting work by the present invention according to the metric compatibility of jet fuel with rubber content of Agidol in kerosene.

This technical result is achieved by the fact that in the known method of determining the quantity of antioxidants in the jet fuel, including exposure of the test jet fuel at 150°C for at least 3 h in a sealed container in contact with the used in the fuel systems of aircraft GTE sealing rubber ring, from which previously removed is introduced into the rubber in the production of antioxidants and which is compressed by 20% it is olsina, fixation based change efforts Fj compression rings from the test duration T, which fixed the maximum compressing force F1after time τ from the time of fixation of a maximum compression force of F1fix this according to the value of the compression force of F2and taking into account the obtained values of F1and F2calculate the metric compatibility WI.the test jet fuel sample rubber, according to the invention the time interval between the fixing F1and F2take equal 3 h, and the compatibility of jet fuel with a rubber sample calculated by the formula:

Wand.t=(F1-F2F1)·100t,h-1

where F1- the maximum force of compression of the sealing rubber rings at 150°C, N;

F2the force of the compression rubber sealing ring at 150°C after a period of time τ from the time of fixation of F1N;

τ=3 h time interval between F1and F2,

then determine the amount of antioxidants in the following is ormula:

C=K1WI.+C2,

where K1=0,007, K2=0 for jet fuel, which WI.from 0 to 10 h-1;

K1=0,002, K2=-0,013 for jet fuel, which WI.>10 h-1.

Figure 1 shows the calibration graph of metric compatibility WEreference samples of jet fuel with rubber on the number WithEAgidol in these samples;

figure 2 - dependence "and" compression force of the sealing rubber rings (at 20% deformation in thickness) from the test time and the dependence of the "b" temperature of jet fuel from the time of the test;

figure 3 - block diagram of the installation to determine the amount of antioxidants found in jet fuel.

For implementing the inventive method of determining the quantity of antioxidants in the jet fuel were used installation and a method for estimating the compatibility of jet fuel with rubber (Patent No. 2475738, 001 No. 33/22).

In the development of the claimed method was obtained a single for the various grades of jet fuel (TS-1, RT, etc.) calibration graph (figure 1) depending on the metric compatibility W jet fuel with rubber on the number of Agidol (the most common antioxidant) in these samples.

To obtain a calibration graph was prepared n reference samples (5-6) each jet fuel, cleansing them from antioxidant is by passing a certain amount of each of them (size n×25 cm 3through an adsorption column filled with alumosilicates, activated for 5 hours at 500°C. In each of n-1 samples have introduced a different number of Agidol in the concentration range of 0.001-0,012% (wt.). For each sample, a reference sample was determined indicator Wecompatibility of jet fuel with a rubber o ring.

The calculation of indicator compatibility W jet fuel with rubber applied the formula, as in the prototype, the maximum compressing force F1a rubber o ring and a compressing force F2(figure 2). However, for the calculation of the indicator compatibility W jet fuel with rubber compression force F2according to the proposed formula was determined after 3 hours of exposure rubber rings in jet fuel, and the formula of prototype - 4 hours.

The results of these determinations are given in table 1.

Table 1
The results of tests on the effect of the concentration of Agidol in the reference samples of jet fuel at the rate W are compatible with sealing ring
No.
p.p
The concentration of Agidol in the reference sample Se % (wt.)
according to the proposed formula
W=F1-F24,N/h
according to the formula prototype
FnHF1HF2HWE, h-1FnNF1HF2*HWEN/h
12345678910
10,012529458a 12.75294589,0
2 0,01244724412,94472447,0
30,01229452812,6294524the 5.25
40,00728432910,02843293,5
50,0052555437,262555403,75
60,0035996844,16 5996823,5
70,0023892852,53892832,25
80,0022850453,32850451,25
90,0023765603,33765601,25
100,0025473663,195473661,75
11 0,001255287821,95287821,25
120,000654478751,284478731,25
130436564,50,25436564,50,125
14031464603146460

From table 1 it follows that the values of WEcalculated by the proposed formula (column 6) in the concentration range above 0,002% (wt.) - 12,7 N; 12,6 N; 12,9 N differed significantly from the values of Wthe calculated by the formula prototype (column 10) - 5.25-inch H; 7,0 N; 9,0 N. When the concentration of the Agidol fuel 0,002% (wt.) and below this influence is not so great. The results of the tests are given in columns 2 and 10 in table 1, indicate that the formula of the prototype correlation between the concentration of Agidol in the fuel (S) and indicator compatibility WEfuel with sealing ring cannot be set.

On the obtained test results (columns 2 and 6 of table 1) build the calibration graph (figure 1) depending on the metric compatibility WEthe jet fuel with rubber content of AgidolEon the x-axis which caused the value of the metric compatibility WI.(point a) of the tested jet fuel with sealing ring, in which the linear dependence found the point B, then on y-axis was determined by the concentration of the antioxidants tested in the jet fuel. According to the results given in columns 2 and 6 (table 1), correlation (calibration) dependence (Fig 1) consists of two linear sections, which are summarized by the formula:

With=K1WI.+C2,

where K1=0,007, K2=0 for WI.from 0 to 10 h-1and

K1=0,002, K2=-0,013 - when values of WI.>10 h-1.

The formula for the coefficients were entered into a computer program.

An example implementation of the proposed method

Box 2 (figure 3) with the carriage 3 raise on the vertical rack 1A up over thermostat and include thermostat 4 to heat up to 150°C. the test sample of jet fuel RT grade of 25 cm3filtered through a filter of "white ribbon" in glass 8 Cup capacity 150 cm3, which is installed in the tank 7. Between the bottom 15 of the hollow cylinder 12 and the movable platform 19 install sealing rubber ring 20 (certain factory party), from which previously removed antioxidant (introduced in the rubber during manufacture), after which it was stored together with other rings in a fully submerged in stable antioxidant kerosene (for example, TS-1 or RT) no more than 35 days. The container 7 is sealed by a cover 10 with welded thereto a hollow cylinder 12, 15 (and a movable thrust 17 inside it), which connect the nuts 23, 24 to the frame 2 on the rack 1A. Through the window 2A connect the two parts of the split thrust 17 and 17A to transfer forces to the compression of the rubber rings 20 on site loading and measuring the force of compression 29-38, located in box 2. In the control unit 39 includes a system of loading a rubber o ring 20, which monitors the movement of the thrust 17, 17A (up), squeezing a rubber o-ring 20 by 20% tol the ins. The compression ring 20 is carried out before touching the bottom 15 of the cylinder 12 with the platform 19. Thus the electrical circuit between the plate 15 and the platform 19 is closed, which leads to the change of direction of thrust 17, 17A (down). At the time of rejection be fixed compression force of the rubber ring 20 (with the deformation of 20% of its thickness) and the change of the direction of movement of the platform 19 (up). This process is carried out automatically at specified intervals. On the computer screen 41 of the control unit 39 settings are displayed according to: a temperature of jet fuel from the test time and "b" is the compression force of the sealing rubber ring F from the time of the test (figure 2).

Within 10-15 minutes at room temperature (tank 7 is located above thermostat) control the initial value Fnthe compression force of the sealing rubber ring 20. If the initial force of the compression rubber sealing ring (Fn=36 N, point a in figure 2) above the critical values of Fn=20 N (for rings of rubber IRP-1078 d=16 mm, H=2 mm), which is indicative of satisfactory workmanship of this ring, the reaction chamber 7 by means of vertical uprights 1A and the carriage 3 is dipped into the nest thermostat 4, heated to 150°C. otherwise, the test stops and are replacing the ring 20 on the other.

P the least heating of the jet force of the compression rubber sealing ring 20 (with ongoing deformation at 20%) increases, and when the temperature reached 150°C and stabilize this temperature increase efforts compression stops and begins its decline. At this time, monitor the presence of excess pressure in the tank 7 by the pressure gauge 14. In his absence the test stop, eliminate leakage of the tank 7, and then repeat the test with another ring 20.

The time to reach maximum values of the compression force of F1=70 N rings (point C on the dependence of "a", figure 2) is fixed with the help of a special program, embedded in the system unit of the computer 40. 3 hours after reaching the maximum value of F1=70 H is automatically fixed the force of the compression ring F2=50 N (point D on the dependence of "a" of figure 2), then on the computer monitor displays the values of Fn=36 N, F1=70 N, F2=50 N, and WI.=9,51 h-1and C=0,00646% (wt.), disables system loading rubber sealing ring 20 and thermostat 4. With vertical racks 1A and the carriage 3, the reaction container 7 is removed from thermostat 4.

Table 2 shows the results of determination of the amount of natural antioxidants in virgin and mixed jet fuel claimed process, as well as Agidol hydrogenated in the jet fuel of the claimed method and chrome-mass spectrometer Varian.

From re is Ulatov, presented in table 2 (columns 7 and 8, lines 12, 14, 15, 17 and 20) shows that the antioxidant content in jet fuel, obtained by both methods are almost the same.

In table. 3 shows examples of the use of the proposed method to obtain the mixed jet fuel with specified quantities of antioxidants. This was mixed in different proportions of two samples of straight-run jet fuel TS-1 and hydrogenates of jet fuel RT with different concentrations of antioxidants in them. The amount of antioxidants in the samples was determined in advance of the proposed method.

From the results shown in table 3 (column 7, 8), it follows that the resulting mixtures measured concentrations of antioxidants practically coincided with the settlement.

In addition, from table 3 it follows that the introduction of straight-run jet fuel TS-1 70% (vol.) unstabilized hydrogenated component (as permitted by NTD) can lead to mixed jet fuel containing anti-oxidants below regulated NTD level, which increases the probability of failure RTI using them to their destination in the engines.

Thus, the application of the proposed method will help:

- to monitor the amount of antioxidants in the jet fuel in their production is ve, application and storage, which will increase the reliability of aircraft operation;

- optimization of the process of increasing the amount of antioxidants in hydrogenated and mixed jet fuel in their production, which will increase the economic efficiency of this process;

- assessing the effectiveness of promising antioxidants in their design.

The method for determining the number of antioxidants found in jet fuel, including exposure of the test jet fuel at 150°C for at least 3 h in a sealed container in contact with the used in the fuel systems of aircraft GTE sealing rubber ring, from which previously removed is introduced into the rubber in the production of antioxidants and which is compressed to 20% of its thickness, fixing dependencies change efforts Fj compression rings from the test duration, which fixed the maximum compressing force F1after a period of time τ from the time of fixation of a maximum compression force of F1fix this according to the value of the compression force of F2and taking into account the obtained values of F1and F2calculate the metric compatibility WI.the test jet fuel sample rubber, characterized in that the time interval between the fixing F1and F2take equal 3 h, and the compatibility of jet fuel with education the CMA rubber are calculated according to the formula

where F1- the maximum force of compression of the sealing rubber rings at 150°C, N;
F2the force of the compression rubber sealing ring at 150°C after a period of time τ from the time of fixation of F1N;
τ=3 h time interval between F1and F2,
then determine the amount of antioxidants according to the following dependence:
C=K1WI.+C2,
where K1=0,007, K2=0 for jet fuel, which WI.from 0 to 10, 0mm;
K1=0,002, K2=-0,013 for jet fuel, which WI.>and 10.0.



 

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2 cl, 7 dwg

FIELD: testing engineering.

SUBSTANCE: device has hydraulic drive which provides reciprocation of the output link, block for control the drive, meter of loading provided with signal converter whose input is connected with the meter, specimen to be tested, passive support, clamps, and rod of hydraulic cylinder.

EFFECT: simplified design.

1 dwg

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