JP-8

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JP-8, or JP8 (for "Jet Propellant 8") is a jet fuel, specified in 1990 by the U.S. government. It is kerosene-based. It is a replacement for the JP-4 fuel; the U.S. Air Force replaced JP-4 with JP-8 completely by the fall of 1996, to use a less flammable, less hazardous fuel for better safety and combat survivability. The U.S. Navy uses a similar formula, JP-5. JP-8 is projected to remain in use at least until 2025. It was first introduced at NATO bases in 1978. Its NATO code is F-34. It is specified by MIL-DTL-83133 and British Defence Standard 91-87.

JP-8 has a flash point of 46 °C (115 °F),[1] compared to -18 °C (0 °F) for JP-4. JP-5 has an even higher flash point of > 60 °C (140 °F), but also a higher cost, limiting its use to aircraft carriers and other situations where the danger of fire is greatest.

Outside of powering aircraft, JP-8 (or JP-5) is used as a fuel for heaters, stoves,[2] tanks,[3] by the U.S. military as a replacement for diesel fuel in the engines of nearly all tactical ground vehicles and electrical generators, and as a coolant in engines and some other aircraft components. The use of a single fuel greatly simplifies logistics.

When used in highly supercharged diesel engines with the corresponding low compression ratio of about only 14:1 or below, JP-8 causes troubles during cold start and idling due to low compression temperatures and following ignition delay because cetane index is not specified in MIL-DTL-83133G to 40 or higher. Because lubricity to the BOCLE method is not specified in MIL-DTL-83133G, modern common rail diesel engines can experience wear problems in high pressure fuel pumps and injectors because of undefined lubricity conditions of this fuel. Another problem in diesel engines can be the increased wear in outlet valve seats in the cylinder heads, because a minimum content of sulfur is not specified in MIL-DTL-83133G. Sulfur in fuels contributes normally to build up damping soot layers in these valve seats. According to the notes in this standard it is intended to install a value for the cetane index in one of the next releases.

Because it does not gel at low temperatures, JP-8 is used at the Amundsen-Scott South Pole Station, for heating, electrical generation, and melting ice for water.

Commercial aviation uses a similar mixture under the name Jet-A.

JP-8 is formulated with icing inhibitor, corrosion inhibitors, lubricants, and antistatic agents, and less benzene (a carcinogen) and less n-hexane (a neurotoxin) than JP-4. However, it also smells stronger than JP-4. JP-8 has an oily feel to the touch, while JP-4 feels more like a solvent. Workers have complained of smelling and tasting JP-8 for hours after exposure. As JP-8 is less volatile, it remains on the contaminated surfaces for longer time, increasing the risk of exposure.[4]

JP-8+100 is a version of JP-8 with an additive that increases its thermal stability by 56°C (a difference of 100°F). The additive is a combination of a surfactant, metal deactivator, and an antioxidant, and was introduced in 1994 to reduce coking and fouling in engine fuel systems. Commercially, this additive is used in Boeing aircraft operated by KLM, and in police helicopters in Tampa, Florida. JP-8+100 is also used for Canadian CF-18 Hornets.

See also

References

  1. ^ [1]
  2. ^ Modern Burner Units, JP-8 is used by Army Food Service Specialists (cooks) to fuel MBUs, in accordance with U.S. Army Field Feeding Manual FM 10-23
  3. ^ the M1 Abrams series of battle tanks uses JP fuel in its gas turbine engine
  4. ^ Day, Dwayne A.. "Aviation Fuel". U.S. Centennial of Flight Commission. http://www.centennialofflight.gov/essay/Evolution_of_Technology/fuel/Tech21.htm. 

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