JP-8+100: The Development of High-Thermal-Stability Jet Fuel

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 not only provides the propulsive energy for flight, but also is the primary coolant for aircraft and engine subsystems. To meet the evolving challenge of improving the cooling potential of jet fuel while maintaining the current availability at a minimal price increase, the U.S. Air Force, industry, and academia have teamed to develop an additive package for JP-8 fuels. This paper describes the development of an additive package for JP-8, to produce “JP-8+100.” This new fuel offers a 55°C (100°F) increase in the bulk maximum temperature (from 325°F to 425°F) and improves the heat sink capability by 50 percent. Major advances made during the development of JP-8+100 fuel include the development of several new quantitative fuel analysis tests, a free radical theory of autooxidation, adaptation of new chemistry models to computational fluid dynamics programs, and a nonparametric statistical analysis to evaluate thermal stability. Hundreds of additives were tested for effectiveness, and a package of additives was then formulated for JP-8 fuel. This package has been tested for fuel system materials compatibility and general fuel applicability. To date, the flight testing has shown an improvement in thermal stability of JP-8 fuel. This improvement has resulted in a significant reduction in fuel-related maintenance costs and a threefold increase in mean time between fuel-related failures. In this manner, a novel high-thermal-stability jet fuel for the 21st century has been successfully developed.

Experimental study of the combustion dynamics of jet fuel droplets with additives in the absence of convection

“…This effort led to development of an additive consisting of blend of a detergent/dispersant (Betz 8Q405, 27.3% (volume percent)), butylated-hydroxyl-toluene (BHT, 9.8%), metal deactivator (MDA, 1.2%), and solvent oil (61.7%) at 256 ppm in JP8. This additive is termed "+100" [2,3]. At the same time, surprisingly little is known about how +100, or other additives for that matter, influences droplet combustion of JP8.…”

“…1 is a schematic of this burning configuration. 2 No prior research on spherical droplet flames of JP8 has been carried out. On the other hand, droplet combustion of JP8 in a strong convective field has been previously studied.…”

“…On the other hand, droplet combustion of JP8 in a strong convective field has been previously studied. Convection was generated during free-fall of droplets in an isothermal vertical furnace [11] (forced convection) or burning of suspended JP8 droplets in a quiescent ambience at 2 Conditions are never as perfect as depicted in Fig. 1.…”

Supercritical Fuel Pyrolysis

“…The fuels used in the next generation of hypersonic aircraft will have to operate under very high pressures and will have to sustain very high heat loads (e.g., > 30,000 BTU/min) in order to meet aircraft cooling requirements [1][2][3]. Predictions indicate that within the fuel lines and injection system, where residence times can be several minutes, fuel temperatures and pressures may reach or exceed 540 °C and 150 atm [2].…”

“…Predictions indicate that within the fuel lines and injection system, where residence times can be several minutes, fuel temperatures and pressures may reach or exceed 540 °C and 150 atm [2]. These ranges of temperature and pressure substantially exceed the critical temperatures and pressures of most pure hydrocarbons and jet fuels such as JP-7 and JP-8 [1,4], so hydrocarbon fuels under these conditions will necessarily be supercritical fluids.…”