Jet fuel
Jet fuel or aviation turbine fuel is a type of aviation fuel designed for use in aircraft powered by gas-turbine engines. It is colorless to straw-colored in appearance. The most commonly used fuels for commercial aviation are Jet A and Jet A-1, which are produced to a standardized international specification. The only other jet fuel commonly used in civilian turbine-engine powered aviation is Jet B, which is used for its enhanced cold-weather performance.
Jet fuel is a mixture of a variety of hydrocarbons. Because the exact composition of jet fuel varies widely based on petroleum source, it is impossible to define jet fuel as a ratio of specific hydrocarbons. Jet fuel is therefore defined as a performance specification rather than a chemical compound. Furthermore, the range of molecular mass between hydrocarbons is defined by the requirements for the product, such as the freezing point or smoke point. Kerosene-type jet fuel has a carbon number distribution between about 8 and 16 ; wide-cut or naphtha-type jet fuel, between about 5 and 15.
History
Fuel for piston-engine powered aircraft has a high volatility to improve its carburetion characteristics and high autoignition temperature to prevent preignition in high compression aircraft engines. Turbine engines can operate with a wide range of fuels because fuel is injected into the hot combustion chamber. Jet and gas turbine aircraft engines typically use lower cost 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 used 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.
Pressure to move from Jet fuel to sustainable aviation fuel, i.e. Aviation biofuel or Electrofuel, has existed since before the 2016 Paris Agreement.
Standards
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. 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. For reasons of inter-operational ability, British and United States military standards are harmonized to a degree. In Russia and the CIS members, grades of jet fuels are covered by the State Standard number, or a Technical Condition number, with the principal grade available being TS-1.Types
Jet A/A-1
Jet A specification fuel has been used in the United States since the 1950s and is usually not available outside the United States and a few Canadian airports such as Toronto, Montreal, and Vancouver, whereas Jet A-1 is the standard specification fuel used in most of the rest of the world, the main exceptions being Russia and the CIS members, where TS-1 fuel type is the most common standard. Both Jet A and Jet A-1 have a flash point higher than, with an autoignition temperature of.Vehicles, pipelines, and storage tanks containing Jet A or Jet A-1 should be marked with black bands, and for vehicles and tanks should also be marked with "Jet A" or "Jet A-1" in white text on a black background.
Differences between Jet A and Jet A-1
The differences between Jet A and Jet A-1 are twofold. The primary difference is the lower freezing point of Jet A-1 fuel:- Jet A's is
- Jet A-1's is
Typical physical properties for Jet A and Jet A-1
Jet A-1 fuel must meet:- DEF STAN 91-91,
- ASTM specification D1655, and
- IATA Guidance Material, NATO Code F-35.
Jet B
Jet B is a naphtha-kerosene fuel that is used for its enhanced cold-weather performance. However, Jet B's lighter composition makes it more dangerous to handle. For this reason, it is rarely used, except in very cold climates. A blend of approximately 30% kerosene and 70% gasoline, it is known as wide-cut fuel. It has a very low freezing point of, and a low flash point as well. It is primarily used in northern Canada and Alaska, where the extreme cold makes its low freezing point necessary, and which helps mitigate the danger of its lower flash point.GOST standards
The GOST standard 10227 specifies civilian fuels, among which are TS-1, T-1, T-1S, T2 and RT. Military fuels such as T-1pp, T-8V and T-6 are specified by GOST 12308. Icing inhibitors are specified by GOST 8313. Some researchers refer to T-6 as "ram rocket fuel"; others have patented a method used to produce T-1pp from a mixture of T-6 and RT, the latter of which has been characterized as "unified Russian fuel for sub- and supersonic aircraft".TS-1
TS-1 is a jet fuel made to Russian standard GOST 10227 for enhanced cold-weather performance. It has somewhat higher volatility than Jet A-1. It has a very low freezing point, below.Additives
The DEF STAN 91-091 and ASTM D1655 specifications allow for certain additives to be added to jet fuel, including:- Antioxidants to prevent gumming, usually based on alkylated phenols, e.g., AO-30, AO-31, or AO-37;
- Antistatic agents, to dissipate static electricity and prevent sparking; Stadis 450, with dinonylnaphthylsulfonic acid as a component, is an example
- Corrosion inhibitors, e.g., DCI-4A used for civilian and military fuels, and DCI-6A used for military fuels;
- Fuel system icing inhibitor agents, e.g., 2-ethanol ; FSII is often mixed at the point-of-sale so that users with heated fuel lines do not have to pay the extra expense.
- Biocides are to remediate microbial growth present in aircraft fuel systems. Two biocides were previously approved for use by most aircraft and turbine engine original equipment manufacturers ; Kathon FP1.5 Microbiocide and Biobor JF. Biobor JF is currently the only biocide available for aviation use. Kathon was discontinued by the manufacturer due to several airworthiness incidents. Kathon is now banned from use in aviation fuel.
- Metal deactivator can be added to reduce the negative effects of trace metals on the thermal stability of the fuel. The one allowable additive is the chelating agent salpn.
it has been necessary for the refiner to optimize the yield of jet kerosene, a high-value product, by varying process techniques.
New processes have allowed flexibility in the choice of crudes, the use of coal tar sands as a source of molecules and the
manufacture of synthetic blend stocks. Due to the number and severity of the processes used, it is often necessary and
sometimes mandatory to use additives. These additives may, for example, prevent the formation of harmful chemical species
or improve a property of a fuel to prevent further engine wear.
Water in jet fuel
It is very important that jet fuel be free from water contamination. During flight, the temperature of the fuel in the tanks decreases, due to the low temperatures in the upper atmosphere. This causes precipitation of the dissolved water from the fuel. The separated water then drops to the bottom of the tank, because it is denser than the fuel. Since the water is no longer in solution, it can form droplets which can supercool to below 0 °C. If these supercooled droplets collide with a surface they can freeze and may result in blocked fuel inlet pipes. This was the cause of the British Airways Flight 38 accident. Removing all water from fuel is impractical; therefore, fuel heaters are usually used on commercial aircraft to prevent water in fuel from freezing.There are several methods for detecting water in jet fuel. A visual check may detect high concentrations of suspended water, as this will cause the fuel to become hazy in appearance. An industry standard chemical test for the detection of free water in jet fuel uses a water-sensitive filter pad that turns green if the fuel exceeds the specification limit of 30 ppm free water. A critical test to rate the ability of jet fuel to release emulsified water when passed through coalescing filters is ASTM standard D3948 Standard Test Method for Determining Water Separation Characteristics of Aviation Turbine Fuels by Portable Separometer.
Military jet fuels
Military organizations around the world use a different classification system of JP numbers. Some are almost identical to their civilian counterparts and differ only by the amounts of a few additives; Jet A-1 is similar to JP-8, Jet B is similar to JP-4. Other military fuels are highly specialized products and are developed for very specific applications.;JP-1
;JP-2
;JP-3
;JP-4
;JP-5
;JP-6
;JP-7
;JP-8
;JP-9
;JP-10
;JPTS
;Zip fuel
;Syntroleum
Piston engine use
Jet fuel is very similar to diesel fuel, and in some cases, may be used in diesel engines. The possibility of environmental legislation banning the use of leaded avgas, and the lack of a replacement fuel with similar performance, has left aircraft designers and pilot's organizations searching for alternative engines for use in small aircraft. As a result, a few aircraft engine manufacturers, most notably Thielert and Austro Engine, have begun offering aircraft diesel engines which run on jet fuel which may simplify airport logistics by reducing the number of fuel types required. Jet fuel is available in most places in the world, whereas avgas is only widely available in a few countries which have a large number of general aviation aircraft. A diesel engine may be more fuel-efficient than an avgas engine. However, very few diesel aircraft engines have been certified by aviation authorities. Diesel aircraft engines are uncommon today, even though opposed-piston aviation diesel powerplants such as the Junkers Jumo 205 family had been used during the Second World War.Jet fuel is often used in diesel-powered ground-support vehicles at airports. However, jet fuel tends to have poor lubricating ability in comparison to diesel, which increases wear in fuel injection equipment. An additive may be required to restore its lubricity. Jet fuel is more expensive than diesel fuel but the logistical advantages of using one fuel can offset the extra expense of its use in certain circumstances.
Jet fuel contains more sulfur, up to 1,000 ppm, which therefore means it has better lubricity and does not currently require a lubricity additive as all pipeline diesel fuels require. The introduction of Ultra Low Sulfur Diesel or ULSD brought with it the need for lubricity modifiers. Pipeline diesels before ULSD were able to contain up to 500 ppm of sulfur and were called Low Sulfur Diesel or LSD. In the United States LSD is now only available to the off-road construction, locomotive and marine markets. As more EPA regulations are introduced, more refineries are hydrotreating their jet fuel production, thus limiting the lubricating abilities of jet fuel, as determined by ASTM Standard D445.
JP-8, which is similar to Jet A-1, is used in NATO diesel vehicles as part of the single-fuel policy.