A Spectroscopic Study of the Reaction Mechanisms of the Oxidation of Metal-Doped exo-Tetrahydrodicyclopentadiene (JP-10) in Levitated Droplets
The primary objective of this project is to unravel the fundamental reaction mechanisms and kinetics involved in the oxidation of JP-10 (exo-tetrahydrodicyclopentadiene) jet fuel, doped with prototype classes of metal-based additives [pre-stressed aluminum (Al), α-aluminum hydride (AlH3), and reactive metal nanopowders (RMNP; Ti-Al, Ti-B, Ti-Al-B)], in the presence of molecular oxygen (O2). These findings will be exploited to develop high-energy-density fuel materials for air breathing ramjet/scramjet applications and as a component in liquid/gel bipropellant rockets. By combining these results with electronic structure calculations, the proposed investigations i) untangle the initial bond breaking and formation processes involving the oxidizer, hydrocarbon, and metal, ii) identify the nature of the primary reaction intermediates, iii) explore the successive isomerization processes of these intermediates, iv) advance the fundamental understanding of the oxidation processes on the most fundamental, microscopic level, v) transform the knowledge of the unimolecular decomposition of chemically activated reaction intermediates and evaluate the processes which control them (energy transfer), vi) establish predictive concepts of (non-adiabatic) reaction mechanisms in metal-doped jet fuel triggered thermally (infrared photons), and vii) illuminate the temperature-and pressure dependent chemical kinetics of the oxidation processes and reveal how metal additives influence and possibly catalyze the underlying reaction mechanism (transition states, overall activation energy). These findings push the boundaries of traditional theory and experimentation revealing energy concepts that are beyond conventional chemistry hence overcoming previous limitations of metal-mediated combustion processes such as the formation of oxide layers.
These objectives are achieved by systematically initiating the reaction and ignition of metal-doped JP-10 in levitated droplets under container-less conditions employing a novel ultrasonic levitation device at combustion-relevant temperatures and pressures. The levitation device represents an emerging laboratory technique, which has not been accessible in previous studies probing the oxidation of JP-10 in the presence of metal additives. To identify the products formed in these processes online and in situ, the levitator incorporates three highly complementary detection schemes eventually revealing the complex reactions and ignition processes of metal-doped JP-10 liquids comprehensively: infrared (IR), Raman (Ra), and ultraviolet – visible (UV-VIS) spectroscopy. By conducting these experiments with levitated droplets of metal- bearing JP-10 and tracing the temporal evolution of the reactants and products on line and in situ spectroscopically, we extract versatile concepts on the decomposition and reaction mechanisms along with the kinetics and products formed in these processes. These data are of crucial significance to understand metal-enhanced combustion processes, the efficiency, and ultimately energy releases of JP-10.