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Experimental determination of the coefficients of viscosity, elasticity and plasticity allows for the theoretical calculations of accuracy, productivity and quality abrasive extrusion processing. Obtained numerical values of the elastic-visco-plastic medium allow the choice of contact of abrasive grains [2]. Having established contact on the proposed methods [3; 4] it possible to calculate the performance of AFM and the roughness of the treated surface details.
Bibliography
1. Левко, В. А. Модель течения рабочей среды при абразивно-экс^узиожой обработке тонких осесимметричных каналов большой длины / В. А. Левко // Вестн.
Чебоксар гое. пед. ун-та. Механика недельного состояния : сб. науч. тр. / под ред. акад. Д. И. ^вдева; Ч^аш. гос. пед. ун-т. Чебоксары, 2008. № 2.P. 85-94.
2. Левко, В. А. Контактные процессы при абразивноэкструзионной обработке / В. А. Левко // Металлообработка. 2008. № 3 (45). P. 19-23.
3. Левко, В. А. Расчет шероховатости поверхности при абразивно-экструзионной обработке на основе модели контактных взаимодействий / В. А. Левко // Авиационная техника. Известия вузов / под ред. проф. В. А. Фирсова ; Казан. гос. техн. ун-т. 2009. № 1.P, 59-62.
4. Levko, V. A. Calculation of surface roughness in abrasive-extrusion machining on the basis of contactinteractionmodel/VA. Levko //RussianAeronautics. N. Y., 2009. Vol. 52, № 1.P. 94-98.
© Snetkov P. A., Levko V. A., Pshenko E. B., Lubnin M. A., 2009
N. F. Orlovskaya, D. A. Shupranov, Yu. N. Bezborodov, I. V Nadeykin SiberianFederal University, Russia, Krasnoyarsk
MODEL-BASED STUDY OF OXIDATION PROCESSES IN A JET ENGINE FUEL LIQUID PHASE
The process of oxidation in hexadecane liquid phase as a conventional model of oil hydrocarbons is investigated. The oxidation product structure is defined by means of Chromatography/Mass Spectrometry.
Keywords: high-temperature oxidation, hexadecane, oxygen-containing organic compounds, jet fuel.
Aviation kerosene is utilized in aircraft engines as a fuel and also as a coolant. Therefore, it should have the property of strong stability against high-temperature oxidation.
It would be of interest to investigate the processes flowing in high-temperaturejet engine fuel oxidation liquid phase.
Hexadecane (HD) is a conventional model of oil hydrocarbons (fig. 1).
12
Fig. l.Hexadecane
Hexadecane behavior in the process liquid phase oxidation was investigated by various authors and by differentways of reactorthermostatting [1].
The term “high-temperature” oxidation is usually applied to the processes flowing at the temperatures of150to170 °C in case ofhexadecane oxidation.
Previous research [1] has established that HD oxidation flowing at high temperature is an exothermal process.
At a certain moment, the so-called time-limited “thermal explosion” takes place in oxidation [1]. After the end of exothermal stage, the oxidation progresses at a lower speed.
Under the assumption [2] it occurs owing to formation of polar nanophase (inverted microemulsion, “water in oil” -type) on the basis of primary and secondary hydrocarbons oxidation products.
The nucleus of such reversed micellar aggregate under the assumption [2] contains a small amount of mono- and polycarboxylic acids and alcohols (polyols). The average sphere includes mainly fragments of ethers and esters. The external sphere consists mainly oflong hydrocarbonchains providing stabilization of micelle in the non-polar hydrocarbon environment (fig. 2).
Changes of the oxidized hydrocarbon phase structure has been experimentally studied [2] indirectly, through a method for water-stain solubilization, for example, methyl-orange (MeOr).
Judging by changes in MeOr band position taking place with a rising hexadecane oxidation degree, the authors [2] have assumed that the localization of stain molecules in the oxidized hexadecane polar nanophase corresponds to a moderately polar oxidation product layer containing chemical bonds of type C-O-C, or similar ones.
Shift ofMeOr absorptionband in the process of increasing hexadecane oxidation degree has been obtained [2].
At the stage of deep oxidation the mechanism of reaction is especially complex. The prime oxidation products are generated. The physical and chemical properties of system are developed and they determine the system operational performance.
If the polar nanophase formation in oxidized hydrocarbons really occurs, the exploitation under heat can result in the formation of a complex colloid structure capable of impacting the flowing processes, on the base of hydrocarbon fuels.
This reasoning gave an impetus to thoroughly study the structure and the dynamics ofhigh-temperature hexadecane oxidation products formation by air oxygen, in a liquid phase.
High-temperature (150to 170 °C) hexadecane oxidation in a liquid phase by air oxygen in a bubbler reactor was carried out through flying products (condensate) selection and with an airbath. It allowed investigating the initial stages of deoxygenation change process in the reaction mixture and condensate following 2,4,5,6,7,8 hours of oxidation.
The oxidation product structure in a condensate and reaction mixture was defined by means of gas chromatography withmass spectrometric detection(GC/MS).
Gas chromatograph-mass spectrometer: Agilent 7890A Gas Chromatograph and 5975C Gas Chromatograph/Mass Spectrometer.
Permanganatometry Method for Hexadecane Oxidation Determination. Thevalue ofAO25 (deoxygenation/absorption of oxygen) corresponds to oxygen milligram quantity absorbed in2ml and conditionally counted on100ml of fuel at 25 °C and the reaction duration of30 minutes [3].
25mlof0.1N Potassiumpermanganate (KMnO4), 10 ml of 20 % sulfuric acid and 2 ml of fuel were placed into a 250-ml glass conical flask with a sealing plug.
The flask was closed up and put into water under the temperature of 25 ± 0,5 °C for 30 minutes, without stirring it up. Upon time being over, the oxidation reaction was terminated through injecting potassium iodide (2 g) with distilled water (100 ml) into the flask. The mixture was stirred up, and the isolated iodine was titrated with 0.1 N sodium thiosulfate Na2S2O3 at presence of 1 ml of 0.5 % starch solution (indicator). The quantity of sodiumthiosulfate was equivalent to the quantity of potassium permanganate not reacted with fuel after 30 minute treatment:
AO25 = 0.8-(a + b)-100/2, where 0.8 - oxygen milligrams isolated by 1 ml of 0.1 N KMnO4 in the acid medium and absorbed by fuel; 2 - mlof fuel introduced into the reaction; 100 - mlof fuel for which the value of value AO25 was conditionally recalculated; a - 25 ml of 0.1 N KMnO, solution introduced into the reaction; b - mlof0.1N Na2S2O3 solution utilized for titration of isolated iodine.
Dimension of AO25: mg 02 /100mlof fuel.
The metrological estimation of the method shows that the maximal deviation from the average parallel definition makes ± 2.0%[3].
Then oxygen absorption was calculated from available data on sodium thiosulfate quantity utilized for titration.
All the data received during experiment are represented in tables 1-3 and the hexadecane mixture reaction and condensate oxidizability were demonstrated through diagrams (figures 3-5):
Hexadecane Oxidation Resistance. As follows from the diagrampresentedinfigure 3, the amountof oxygen-containing compounds in the reactor eventually increases, and in the condensate the amount decreases. Probably it is explained by the fact that substances with greater molecular weight are formed during high-temperature oxidation.
Intheoxidationofparaffins, compoundswithamore complex chemical structure than simple acids (ketones, aldehydes, spirits orhydroperoxides), are always found. Occurrence of more oxidized products (for example, lactones) is not necessarily consequence of repetitive oxygenattackuponthe products already containing oxygen. Similaroxidizedproductsareformedattheminimaldepth of conversion, too. Lactones are internal complex esters of hydroxy acids. Hydroxy acids are easily dehydrated at higher temperatures. Among the oxidationproducts, formationboth y-, and 8-lactones could be observed.
High-temperature (150-170 °C) hexadecane oxidationwith air oxygen was investigated in a liquid phase as a model of hydrocarbonjet engine fuel, with sampling condensate and reactionmixture.
Values of AO25 parameter (absorption of oxygen) of reaction mixture and condensate received through hexadecane high-temperature oxidation were determined by permanganatometry.
The oxidationproduct structure was identifiedby means of a gas chromatography with mass spectrometric detection (GC/MS).
It was established that the amount of oxygen-containing compounds in the reactor eventually increases, and in condensatetheiramountdecreases. Probably, substanceswith greater molecular weight are formed during high-temperature oxidation. Additional research are required to induce the law.
Among the hexadecane oxidation products, identified were: spirits, carbonyl compounds, carbon acids, esters of carbon acids and lactones (internal esters of r- and a-hydroxy carbon acids). Similar compounds can be a part of turned
\
O O OOH
OH
OOH ■V'*'1'
OOH
O
Fig. 2. Presumable structure of polar nanophase in the oxidized hydrocarbons
micellar aggregates, which impact upon physical and chemical properties and operational performance ofjet engine fuels.
Bibliography
1. Influence of Conditions of Liquid-phase High-temperature Hexadecane Oxidation upon the Process Mechanism/E.Y. Oganesova [etal.] //Petro-chemistry. 2GG4. Vol. 44. No. 2. P. 119—12б. (inRussian)
2. Condition ofFormation and Properties ofHexadecane OxidationProductMicelle Structure StudiedthroughaMethod forWater-stain Solubilization/E. Y. Oganesova [et al.] //Petrochemistry. 2005. Vol. 45. No. 4. P. 294-300. (inRussian).
3. C.c. 750373 USSR, MCI3 G 01 N 33/22.Away of Estimation for Oxidability and Degree of Oxidizability Engine Fuel and Their Components /Ya. B. Tchertkov, T. I. Kirsanov (USSR). - No. 2628862/23-04; declared 15.06.78; published 23.07.80.Bull.No. 12. -6p. (inRussian)
Table 1
Results of AO25 Reaction Mixture and Condensate Determination Received at High-temperature Hexadecane Oxidation
Time of oxidation, h Reaction mixture, AO25, mg 02/lGG ml Condensate, AO25, mg 02/lGG ml
2 4В бВ4
4 80 66G
5 72 59б
б бВ 524
7 12В 472
В 9б 512
Table 2
Results of Chemical Composition Determination for Reaction Mixture Received at Hexadecane High-temperature Oxidation
№ Oxygen-containing compound Amount, %
1 Heptanal 4.5б
2 5-Methyl-2(3H)dihydrofuranon 2.2G
3 Hexanoic acid 2.2В
4 2,6 -Dihydropyranon-2 1.G5
5 5-Ethyl-2(3H)dihydrofuranon 1.5G
б Heptanoic acid 4.В4
7 y-Lactone 4-hydroxyheptanoic acid 2.49
В Octanoic acid 7.72
9 8-Lactone 5-hydroxyoctanoic acid 3.3G
1G y-Lactone 4-hydroxynonanoic acid 2.95
11 Decanoic acid 13.17
12 y-Lactone 4-hydroxydecanoic acid 15.G5
13 2-Undecanone 1.59
14 Dodecanoic acid В.15
15 Tridecanoic acid З.ЗВ
1б y-Lactone 4-hydroxydodecanoic acid 3.GG
17 Tetradecanoic acid 1.71
1В 5 -Pentadecanone 4.99
19 2-Nonadecanone б.ВЗ
2G Pentanoic acid, tridecyl ester 2.34
21 6-Dodecanone 3.G6
Table 3
Results of Chemical Composition Determination for Condensate Received at High-temperature Hexadecane Oxidation
№ Oxygen-containing compound Amount, %
1 Decanoic acid 1.б4
2 Undecanoic acid 2.19
3 Dodecanoic acid З.б5
4 y-Lactone 4-hydroxyundecanoic acid 5.3б
5 Tridecanoic acid 4.94
б y-Lactone 4-hydroxydodecanoic acid 3.99
7 Tetradecanoic acid 5.7б
В 7 -Pentadecanone 6.4G
9 4-Hexadecanone 4.72
1G 1-Tridecyn-4-ol 4.G6
11 3-Hexadecanone 4.б2
12 2-Hexadecanone б.24
13 2-Heptadecanol 2.1В
1G5
AOfcejfflf O2/IOO nil
Time of oxidation, h
Fig. 3.Values ofAO25 parameter (absorption of oxygen) in reaction mixture and condensate
■ AO of reaction mixture
■ AO of condensate
Time of oxidation, h
Fig.4. Comparison ofAO25 parameter (absorption of oxygen) for reaction mixture and condensate
■ AO of condensate
■ AO of reaction mixture
2 4 5 6 7 S
Time of oxidation, h
Fig. 5. The totalAO25 parameter
© Orlovskaya N. F., Shupranov D. A., Bezborodov Yu. N., Nadeykin I. V., 2009
