Determination of fractional composition of jet fuel

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THE MINISTRY OF SCIENCE AND EDUCATION OF UKRAINE

NATIONAL AVIATION UNIVERSITY

INSTITUTE OF ECOLOGICAL SAFETY

HOMEWORK

“Determination of Fractional Composition of Jet Fuel”

On discipline:

“QUALITY CONTROL OF FUELS AND LUBRICANTS”

Performed by: Nitsak T.S.

Checked by: Chernyak L. M.

KYIV 2014

Content

1. Jet fuel

1.1 General information

1.2 Properties

2. Fractional composition

2.1 Importance

2.2 Fractional composition of jet fuel

2.2.1 Initial boiling point and 10% fuel distillation temperature

2.2.2 50% fuel distillation temperature

2.2.3 Temperature of 90 % fuel distillation (t₉₀) and dry point

3. Fractional composition GOST

4. Testing

4.1 Device for determination

4.2 Performance

References

1. Jet fuel

1.1 Definition

The jet fuel used in jet aircraft engines. The most common jet fuels are kerosine fractions obtained by straight-run distillation of low-sulfur and high-sulfur crude oils; examples of these fuels are the domestic jet fuels T-l (from low-sulphur crude oil) and TS-1 (from high-sulphur crude oil). Fuels with high thermal stability, such as the domestic fuel RT and the foreign fuels A, A-l, and B, are manufactured by hydrofining fractions derived from straight-run distillation. Other components used in the production of jet fuels are obtained by hydrocracking and the removal or conversion of mercaptans.

Fuel for piston-engine powered aircraft (usually a high-octane gasoline known as avgas) has a low flash point to improve its ignition characteristics. Turbine engines can operate with a wide range of fuels, and jet-aircraft engines typically use fuels with higher flash points, which are less flammable and therefore safer to transport and handle.

The first axial compressor jet engine in widespread production and combat service, the Junkers Jumo 004 on the Messerschmitt Me 262A fighter, and the Arado Ar 234B jet recon-bomber, burned either a special synthetic "J2" fuel or diesel fuel. Gasoline was a third option but unattractive due to high fuel consumption. Other fuels used were kerosene or kerosene and gasoline mixtures. Most jet fuels in use since the end of World War II are kerosene-based. Both British and American standards for jet fuels were first established at the end of World War II. British standards derived from standards for kerosene use for lamps--known as paraffin in the UK--whereas American standards derived from aviation gasoline practices. Over the subsequent years, details of specifications were adjusted, such as minimum freezing point, to balance performance requirements and availability of fuels. Very low temperature freezing points reduce the availability of fuel. Higher flash point products required for use on aircraft carriers are more expensive to produce.^[3] In the United States, ASTM International produces standards for civilian fuel types, and the U.S. Department of Defense produces standards for military use. The British Ministry of Defence establishes standards for both civil and military jet fuels.^[3] For reasons of inter-operational ability, British and United States military standards are harmonized to a degree. In Russia and former Soviet Union countries, grades of jet fuels are covered by the State Standard (GOST) number, or a Technical Condition number, with the principal grade available in Russia and members of the CIS being TS-1.

1.2 Properties

The most important properties of a jet fuel are its density and heat of combustion (see Table 1), which determine the flight range. A jet fuel should have high thermal stability, particularly if it is to be used in supersonic aircraft, where the temperature of the fuel in the tanks may exceed 150°-200°C. High thermal stability is attained by removing nonhydrocarbon impurities, such as sulfur, nitrogen, and oxygen compounds, from the fuel, for instance, by hydrogenation. Such processing also ensures that the jet fuel will have low corrosiveness.

In order to improve the stability of refined fuels during storage, antioxidants (up to 24 mg/liter) and additives to deactivate metals (6 milliliters/liter) are used. Jet fuels contain dissolved water (up to 0.008-0.01 percent at normal temperatures), which can separate from the fuel as conditions change, causing electrochemical corrosion in the fuel system or the formation of ice crystals. For this reason, corrosion inhibitors (10-45 mg/liter) and deicing additives (0.1-0.3 percent by volume) are used. Other additives prevent the accumulation of static electricity and improve the wear-inhibiting qualities of the fuel.

fuels fractional distillation temperature

Table 1. Basic physical and chemical characteristics of jet fuels manufactured in the USSR

2. Fractional composition

Hydrocarbon fuel is a liquid of complex composition consisting of many individual hydrocarbons. Such mixtures have no definite boiling temperatures during distillation, and the process of boiling occurs in some range of temperatures. It is accepted to characterize evaporability of liquids of complex composition with their fractional composition (boiling range distribution), i.e. with the certain limiting temperatures of boiling of the specific volumetric parts (fractions).

Distillation can be of two kinds: simple distillation and rectification. Three types of distillation is distinguished based on the conditions at which the process is conducted: atmospheric, lowered pressure (vacuum), and with water vapour.

Fractional distillation is one of the major fuel parameters, describing fuel evaporability. Fractional distillation of fuel is defined by the distillation method, which is based on a principle of gradual evaporation without rectification at atmospheric pressure following a standard procedure according to ГОСТ 2177 (ASTM D 86, ISO 3405). Process of distillation requires:

- temperature of initial boiling (t_ib), 10, 50, 90, and 97,5 % (dry point) fuel distillation (for gasoline);

- temperature of initial boiling (t_ib), 10, 50, 90, and 98 % (dry point)fuel distillation (for jet fuel).

2.1 Importance

Fuels must be easily convertible from storage in the liquid form to the vapor phase in the engine to allow formation of the combustible air-fuel vapor mixture. This ability of fuel is called evaporability. It determines reliability, efficiency and durability of engine operation at different regimes, including its easy or complicated start, fast and slow warming up, acceleration, completeness of combustion and fuel combustion character, amount of deposit formation in the engine, vapor locks formation in the fueling system, and also the losses due to evaporation during transporting, pumping, and storage of fuel.

If gasoline fuel volatility were too low, liquid fuel would enter the cylinder and wash lubricating oil from the walls and pistons and so lead to increased engine wear; a further effect would be to cause dilution of the crankcase oil; poor volatility can also give rise to poor distribution of mixture strength between cylinders. Conversely, if volatility is too high, the fuel can vaporize in the fuel tank and supply lines, giving undue venting losses and the possibility of fuel starvation through vapor lock in the fuel lines. The cooling effect due to rapid vaporization of excessive amounts of highly volatile materials can also cause ice formation in the carburetor under certain conditions of humidity and air temperature.

2.2 Fractional composition of jet fuel

2.2.1 Initial boiling point and 10% fuel distillation temperature

Fuel starting properties (startability) depend on the content of light fractions in it, which is determined by initial boiling and 10 % fuel distillation temperatures. The lower the temperature of the environment is, the more light fractions are needed for engine start. This parameter has a great importance especially for jet fuels in the case of a need for dead engine restart during the flight. However excessive amount of low-boiling fractions in the composition of fuel may cause malfunctions of the work of overheated engine through vapor locks formation in fuel supply system. This phenomenon is especially common for hot climate conditions. Physical stability (inclination to fuel loss through evaporation) also depends on the amount of light-boiling fractions.

2.2.2 Temperature of 50 % fuel distillation (t₅₀)

Temperature of 50 % fuel distillation (t₅₀) has the biggest influence on the speed of engine's warming up time, stability of operating at low rotation numbers, acceleration, and the wear of cylinder-piston group. It reflects the amount of intermediate fractions in the fuel. Acceleration (Ukr. прийомистість) is the rapidity of change in engine operating regime toward rotation increase. The lower the t₅₀, the better fuel evaporates and the higher the speeds of acceleration and engine's warming up are (and, therefore, the fuel expenditure decreases). However, if the t₅₀ is lowered too much, possible ice formation in carburetor may arise.

2.2.3 Temperature of 90 % fuel distillation (t₉₀) and dry point

Temperature of 90 % fuel distillation (t₉₀) and dry point are characteristics of completeness of evaporation of fuel and evenness of fuel-air mixture distribution in engine's cylinders. If the dry point is greater than predetermined temperature, the fuel does not combust completely, its expenditures, deposit formation and wear of engine increase, and effectiveness and power of engine decrease.

3. Fractional composition GOST

Ukrainian standards ГСТУ 320.00149943.007-97 “Fuel for jet engines RT. Technical requirements” and ГСТУ 320.00149943.011-99 “Fuel TS-1 for jet engines. Technical requirements” set the following boiling range distribution for RT and TS-1 fuels:

4. Testing

4.1 Device for determination of fractional composition.

Fraction distillation of fuel is performed with the help of the special device .

The device for determination of fractional composition of fuels (АРН-ЛАБ-02) 1 - thermometer; 2 - still pot; 3 - asbestos spacer; 4 - electrical heating element; 5 - stand; 6 - still pot position regulation handle; 7 - heating regulation control; 8 - switch; 9 - cover unit bottom; 10 - graduated cylinder; 11 - filtering paper; 12 - cooling bath; 13 - condenser line; 14 - cover unit

4.2 Performance

100 ml of the dehydrated petroleum product is measured with a dried and clean graduated cylinder. Read the quantity of a product by the bottom edge of meniscus.

Pour the petroleum product into a rinsed with light petrol and air-dried flask, so that the liquid does not get in the pipe bend of the flask. Put one or two 2 mm small chips of holystone (boilers) into the flask to ensure not too rough boiling. The flask is closed by a stopper, through which a thermometer is inserted, so that the top edge of the mercury head will be placed at the level of the bottom edge of the flask bend. Then, the flask is put on asbestos lining and covered with a metal casing. Wipe the tube of the cooler with a cloth and connect the flask pipe bend with a stopper to the cooler so that the flask pipe bend will enter the tube the cooler at 25-40 mm and does not touch its walls. The flask should stand on a lining strictly vertically, the thermometer should be established also vertically in the flask. The graduated cylinder, which serves for receiving the petroleum products without being dried up, is put under the end of the cooler tube and covered with a cotton wool. The tube of a cooler should enter into the cylinder no less than for 25 mm but not lower than the mark of 100 ml. For gasoline the temperature of water in the cooler should be 0- -1 °C, and for jet fuels and diesel fuels it should not differ for more than 3°C from the temperature of environment.

Turn on the heating. The heating is adjusted so that the first drop of condensate will fall during the distillation not earlier than in 5 min, and not later than in 10 min for gasoline; and during the distillation of jet fuel - not earlier, than in 10 min, and not later than in 15 min.

Temperature, which is shown by the thermometer when the first drop falls in the receiver, is read as a beginning boiling point. After that adjust distillation speed so that every two drops will fall in 1 sec. (no less than 4 ml and no more than 5 ml in a minute). The observance of distillation speed is the most important part of work; if it is not observed properly, the results received will be incorrect.

After the determination of temperature of initial boiling, the graduated cylinder is moved relatively the end of the cooler tube, so that the distillate will pass on the wall of the cylinder. During the check of speed of distillation by quantity of drops, the end of the cooler tube should be at the centre of the cylinder.

While distillation one must record the temperatures at which the distillate volume is reaching 10, 20, 30, 40, 50, 60, 70, 80 and 90 % accordingly, and depending on specifications for a fuel one should determine temperature of 97,5 or 98 % fuel condensation or temperature of the distillation end. When the final temperature specified in the specifications for the testing petroleum products (for light fuels the temperatures of distillation correspond to 96, 97,5 or 98 %) is achieved, the heating of the flask stops, then distillate is allowed to flow down during 5 min and volume of a liquid in the cylinder is finally recorded.

During distillation of the fuel T-l, TC-1, T-2 and kerosene, which can boil away before achievement of the temperature stipulated in the specifications for 98 % volume boiling off, distillation is allowed to stop from the moment when the level of the liquid in the cylinder reaches 97,5 mL, then the flask heating is stopped and the temperature is recorded. Then distillate is given possibility to flow down during 5 min, and volume of liquid in the cylinder is recorded. If volume of a liquid in the cylinder is less than 98 mL, the distillation should be repeated.

References

“Nefteprodukty”, B.V. Losikov, Moskow, 1966;

“Zarubezhnye topliva masla I prisadki”, I.V.Roshkov, B.V. Losikov, Moskow, 1966;

"Beginner's Guide to Aviation Biofuels". Air Transport Action Group. May 2009.

“The History of Jet Fuel” Air BP

“Fuel Property, Emission Test, and Operability Results from a Fleet of Class 6 Vehicles Operating on Gas-To-Liquid Fuel and Catalyzed Diesel Particle Filters Yosemite Waters-Vehicle Evaluation Report” - National Renewable Energy Lab

"Handbook of Products". Air BP.

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