Gaseous Detonations. V. Nonsteady Waves in CO–O2 Mixtures

Abstract

The velocity of steady detonation waves in 2.5 CO–O2 mixtures containing hydrogen agrees with the calculations of the Chapman-Jouguet theory. When all sources of hydrogen atoms are eliminated from such mixtures, much hotter shock waves must be used to initiate detonation. The detonation waves in hydrogen-free mixtures are stable but nonsteady. The velocities observed by piezoelectric pressure gauges undergo violent and not very regular fluctuations similar to, but not identical with, spinning detonations. Moving film slit photographs show that these fluctuations are caused by detonation fronts developing behind the forward shock, overtaking it at irregular intervals, and decaying in their stead. Similar detonation fronts are observed in delayed initiations of explosive mixtures capable of stationary detonation, but the waves upon initiation and after a few fluctuations settle into the stationary Chapman-Jouguet regime. Photographic observations show that the detonations developing behind the shock front are initially localized near the opposite walls of the cylindrical tube, while the guage records demonstrate that the fronts of nonsteady waves are not normal to the tube axis but undergo irregular girations. The significance of these observations in terms of the rates of chemical reactions in shock fronts is discussed.