Liquid-Fueled Detonations in Tubes

Motivated by the current interest in pulse detonation engines, a brief review of previous work on liquid-fueled detonations in tubes is presented. Although the characteristics of detonations in high-vapor-pressure liquid fuels are analogous to those of gaseous detonations, the behavior of detonations in low-vapor-pressure liquid fuels is quite different. The multidimensional structure and the cell sizes of such mixtures have not yet been established. Theoretical, computational, and experimental studies have shown that if the droplets are fine enough (less than about 10 μm), detonations propagating at about the equivalent gas-phase Chapman‐Jouguet detonation velocity can be attained in a variety of fuel‐oxygen systems. With larger droplet sizes, a deficit in the propagation velocity compared to the gas-phase velocity is observed. Various explanations for this deficit are presented. The droplet size required for detonations in fuel‐air mixtures is smaller than that in fuel‐oxygen mixtures. Heating the initial mixture helps both by easing the detonation initiation process and by aiding in the detonation propagation by introducing some prevaporization and reducing the droplet size. The need for additional research on multiphase detonations to aid in the further development of liquid-fueled detonation engines is also emphasized.