JP-7
JP-7 (abbreviation for J et P ropellant 7 , specification according to MIL-T-38219 ) is a fuel for aviation applications that was developed by the US Air Force to operate aircraft that heat up considerably due to air friction. Essential characteristics are high flash point and high boiling point. It essentially consists of high-boiling alkanes and cycloalkanes .
The development of this fuel was initiated by James Harold Doolittle , who worked at Shell , following a request from Lockheed . Together with Ashland , Monsanto and Pratt & Whitney , the development initially led to a fuel called LF-2A ( Lockheed Lighter Fluid 2A ), which was designated by the USAF as PF-1. In 1970 the further developed JP-7 fuel emerged from this.
For many years the fuel was used exclusively on the Lockheed SR-71 . The only engine at the time that was designed for this fuel was the Pratt & Whitney J58 . On May 26, 2010, the Boeing X-51 flew with synthetically manufactured JP-7 for the first time . The proportion of volatile components such as aromatics , benzene and toluene is only 3%. The fuel is practically free of sulfur, oxygen and nitrogen impurities.
In addition to hydrocarbons, fluorocarbons (type: PWA-536) with 0.2–0.25% were added to improve lubricity. This addition also made it possible to use the fuel as hydraulic fluid .
JP-7 is difficult to ignite by conventional means. That is why the SR-71 was used to ignite the fuel in the combustion chamber of the J58 engines using triethylborane as a chemical igniter. When P & W Rocketdyne-SJY 61-2 -Triebwerk the Boeing X-51 burns first ethylene , then the combustion in JP-7 is converted.
| parameter | value |
|---|---|
| Pour point | −30 ° C |
| boiling point | 282-288 ° C |
| Density (at 15 ° C) | 779-806 kg / m³ |
| Vapor pressure (at 149 ° C) | 20.7 kPa |
| Flash point | 60 ° C |
| Calorific value | min. 43.5 MJ / kg |
| viscosity | 10 centistokes at −40 ° C |