Two-dimensional unconfined gaseous detonation waves

Abstract

The distribution of the fluid properties behind a steadily expanding cylindrical detonation wave is determined by solving the basic equations for the unsteady expansion of the combustion products. An unconfined cylindrical Chapman-Jouguet detonation wave is found to be non-existent at small radius, and must propagate as either a strong detonation ( D < U 1 + C 1 ) or a weak detonation ( D > U 1 + C 1 ). Direct initiation of a cylindrical detonation wave requires the instantaneous release of a large quantity of ignition energy. Measurements of the detonation pressure at different radii show that a cylindrical detonation wave is initially overdriven, and decays rapidly with increasing radius to a Chapman-Jouguet wave. Under normal circumstances, true transition from cylindrical deflagrations to detonations are not observed. Pseudo-transition, a result of the interaction of the reflected precompression waves off the cylindrical wall with the flame, occurs when a significant amount of normal burning has been completed. Transitions from cylindrical deflagrations to detonations are observed when turbulence is artificially generated by introducing a spiral coil on one of the inner faces of the cylindrical vessel. Cylindrical retonation waves are always observed at the onset of detonation. Spinning and pulsating cylindrical detonation waves are not observed near the limits of detonability.