Advanced Jet Fuels — JP-4 Through JP-8 and Beyond

Abstract

Jet fuel requirements have evolved over the years as a balance of the demands placed by advanced aircraft performance (technological need), fuel cost (economic factors), and fuel availability (strategic factors). In a modern aircraft, the jet fuel is the primary coolant for aircraft and engine subsystems and provides the propulsive energy for flight. To meet the evolving challenges, the U.S. Air Force, industry and academia have teamed to develop new and improved fuels that offer increased heat sink and thermal stability, properties that will enable improved aircraft design and decrease fuel system maintenance due to fuel fouling/coking. This paper describes the team effort to develop improved JP-8, named “JP-8+100”, that offers a 55C (100F) improvement in thermal stability and a 50% increase in heat sink. The government, industry, and academia team has made numerous advances in the development of JP-8+100 with a more complete understanding of the fundamental processes of deposition, new approaches to reducing fouling/coking, and new tests and models to assist the designers of aircraft and engine fuel systems. Some of the principal advances are: new quantitative research devices and fuel system simulators that provide thermal stability information that cannot be obtained using the standard JFTOT test; new techniques to measure oxygen consumption and fuel degradation pathways; a free radical theory to explain behaviors such as the inverse relationship between thermal and oxidative stability, advanced CFD models with coupled degradation chemistry, and a new thermal stability ranking scale for jet fuels. The insight obtained has been applied to the development of an additive package for JP-8 that shows thermal stability improvements equal to or greater than the stated goal and enables the development of even higher thermal stability fuels such as JP-900.