Single-Cycle Performance of Idealized Liquid-Fueled Pulse Detonation Engines

Abstract

Single-cycle performance estimates of an idealized liquid-fueled pulse detonation engine (PDE) are derived from numerical simulations of detonation of JP-10 fuel droplets in oxygen and in air. Results for a range of fuel droplet sizes, as well as results when some of the fuel is prevaporized, are discussed. For JP-10‐O2, calculations indicate that fuel-based specific impulse is comparable between different cases when the detonation is fully developed by the time it reaches the end of the detonation tube. Time-dependent thrust results, however, depend significantly on the initial form of the fuel. Degradation in total performance occurs when droplet sizes are so large that full transition to a self-propagating state cannot be reached by the end of the tube. For JP-10‐air mixtures, results are similar, but stricter constraints on droplet size and prevaporization level for near-full performance exist. (Smaller droplet sizes and higher levels of prevaporization are required.) Introduction of some initial vapor fuel or heating of the detonation tube extends the droplet size limits at which near-full performance is obtained. More generally, results suggest that, for small enough droplets and/or with sufficient prevaporization of the fuel, liquid-fueled PDEs will provide comparably efficient single-cycle propulsive performance to gaseous fueled PDE devices. Nomenclature A = cross-sectional area of detonation tube Bi = transfer number of the ith droplet C Di = drag coefficient of the ith droplet c p = heat capacity of the gas at constant pressure c p,v = heat capacity of the fuel vapor at constant pressure cv = heat capacity of the gas at constant volume d pi = diameter of the ith droplet