Jet fuels

Petroleum is the mixture of gaseous, liquid, and solid hydrocarbons (although the term is often restricted to the non-gases) derived from chemical reactions on prehistoric animal and vegetable matter which occurs as reservoirs in sedimentary rocks from which it is extracted. Petroleum (8002-05-9) syn. crude oil or petroleum oil also contains inorganics such as compounds of sulphur, nitrogen, oxygen, metals, etc. 

Natural gas (8006-14-2) is the gaseous component of petroleum. It is mostly methane with some ethane and smaller quantities of propane, butane, carbon dioxide, hydrogen sulphide, nitrogen, helium, and other gases. It is distributed in commerce as compressed or liquefied natural gas (LNG) for fuel and other purposes. 

Crude oil is processed in refineries by distillation, cracking, reforming, alkylation, polymerization, and other methods to generate gases, distillates, residuum, and sludges from which an enormous number of petroleum products 

The author was unable to find a reference for why an oil well sampling device might be charged with a compressed or liquefied gas. 

In addition to natural gas a number of gases are associated with petroleum  

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Lamp Method the sample is burned in a closed system in an atmosphere of 70% CO2 and 30% oxygen in order to avoid formation of nitrogen oxides. This method was to have been abandoned as it takes three hours to carry out, but remains officially required for jet fuel sulfur analysis. 

First of all, a technical clarification is necessary in the wider sense, motor fuels are chemical compounds, liquid or gas, which are burned in the presence of air to enable thermal engines to run gasoline, diesel fuel, jet fuels. The term heating fuel is reserved for the production of heat energy in boilers, furnaces, power plants, etc. 

In the expression for heating value, it is useful to define the physical state of the motor fuel for conventional motor fuels such as gasoline, diesei fuel, and jet fuels, the liquid state is chosen most often as the reference. Nevertheless, if the material is already in its vapor state before entering the combustion system because of mechanical action like atomization or thermal effects such as preheating by exhaust gases, an increase of usefui energy resufts that is not previously taken into consideration. 

There are several types of jet fuels according to their civilian or military application, their names can vary from one country to another. 

The most widely used product is TRO (TR for turbo-reactor) or JP8 (JP for Jet Propulsion), still designated by the NATO symbols F34 and F35. In the United States, the corresponding fuel is called Jet Al. The military sometimes still uses a more volatile jet fuel called TR4, JP4, Jet B, F45 or F40. The preceding terms correspond to slight variations and it would be superfluous to describe them here. 

There is finally another type of jet fuel somewhat heavier and less volatile than TRO, which allows safe storage on aircraft carriers. This is the TR5 or JP5. Among these products, TRO or Jet Al have the most widespread acceptance because they are used for almost all the world s civil aviation fleet. The information that follows will concern essentially TRO, and very rarely TR4. 

The luminometer index (ASTM D 1740) is a characteristic that is becoming less frequently used. It is determined using the standard lamp mentioned above, except that the lamp is equipped with thermocouples allowing measurement of temperatures corresponding to different flame heights, and a photo-electric cell to evaluate the luminosity. The jet fuel under test is compared to two pure hydrocarbons tetraline and iso-octane to which are attributed the indices 0 and 100, respectively. The values often observed in commercial products usually vary between 40 and 70 the official specification is around 45 for TRO. 

Luminometer index for the combustion flame of a jet fuel as a function of its volumetric content in aromatics. 

Solubility of water in jet fuels as a function of temperature (Jet A is a variant] of Jet Al, used in the USA for domestic flights. Jet A has a freezing point higher than that of Jet Al). ... 

Fuel passing through certain hot zones of an aircraft can attain high temperatures moreover it is used to cool lubricants, hydraulic fluids, or air conditioning. It is therefore necessary to control the thermal stability of jet fuels, more particularly during supersonic flight where friction heat increases temperatures in the fuel tanks. 

The most common technique for estimating thermal stability is called the Jet Fuel Thermal Oxidation Test (JFTOT). It shows the tendency of the fuel to form deposits on a metallic surface brought to high temperature. The sample passes under a pressure of 34.5 bar through a heated aluminum tube (260°C for Jet Al). After two and one-half hours, the pressure drop across a 17-micron filter placed at the outlet of the heater is measured (ASTM D 3241). 

The stocks used for jet fuel production come almost essentially from direct distillation of crude oil. They correspond to the fraction distilled between 145 and 240°C, more or less expanded or contracted according to the circumstances. The yield of such a cut depends largely on the nature of the crude but is always larger than the demand for jet fuel which reaches about 6% of the petroleum market in Europe. For the refiner, the tightest specifications are ... 

Finally, note that hydrocracking is ideal for obtaining middle distillate cuts that can be used in jet fuel formulation. 

The properties linked to storage and distribution do not directly affect the performance of engines and burners, but they are important in avoiding upstream incidents that could sometimes be very serious. We will examine in turn the problems specific to gasoline, diesel fuel, jet fuel and heavy fuel. 

Jet fuel is subject to particular attention in all operations that precede and accompany its use in accordance with the draconian air transport safety regulations (Anon., 1983). 

Leaving the refinery, jet fuel has generally no free water and contains only a small quantity of dissolved water. But humidity from the air and tank breathing result in continuous intrusion of water that must be then removed by decanting and filtration. This is why jet fuel needs to be tested for its ability to separate the contained water. 

For jet fuels, the elimination of free water using filters and coalescers by purging during storage, and the limit of 5 ppm dissolved water are sufficient to avoid incidents potentially attributable to water contamination formation of micro-crystals of ice at low temperature, increased risk of corrosion, growth of micro-organisms. 

However, of all the petroleum products, jet fuel is the one receiving the most careful scrutiny. 

Until 1992, the total sulfur content of jet fuel was limited to 0.2 wt. %. Starting in 1993, a reduction to 0.1% was instituted apparently without major incident since for commercial products, lower levels (to 500 ppm) had been observed very often. 

Finally, other tests to control jet fuel corrosivity towards certain metals (copper and silver) are used in aviation. The corrosion test known as the copper strip (NF M 07-015) is conducted by immersion in a thermostatic bath at 100°C, under 7 bar pressure for two hours. The coloration should not exceed level 1 (light yellow) on a scale of reference. There is also the silver strip corrosion test (IP 227) required by British specifications (e.g., Rolls Royce) in conjunction with the use of special materials. The value obtained should be less than 1 after immersion at 50°C for four hours. 

An fuel-air mixture explosion can be initiated by a sudden discharge of static electricity. Yet, while flowing in systems, a fluid develops an electrical charge which will take as long to dissipate as the fluid is a poor conductor. The natural electrical conductivity of jet fuel is very low, on the order of a few picosiemens per meter, and it decreases further at low temperature. 

It is believed that to avoid any risk of explosion, the electrical conductivity of jet fuel should fall between 50 and 450 pS/m. This level is attained using anti-static additives which are metallic salts (chromium, calcium) added at very low levels on the order of 1 ppm. 

Specifications and test methods for jet fuel. The specifications of jet fuels are set at the international level and are written into the Aviation Fuel Quality Requirements for Jointly Operated Systems". 

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