On the Influence of Tube Diameter on the Development of Gaseous Detonation

Abstract

AbstractStreak photographs of the transition from slow‐burning to detonation have been obtained by self‐light photography of the flame using a rotating drum camera. Experiments were performed with stoichiometric hydrogen‐oxygen mixtures contained in plastic tubes closed at one end and ignited by pilot flames. The investigation included the effect of tube diameter and distance of ignitor from closed end on the development of detonation.The plots of detonation induction distances and times as a function of tube diameter indicate the existence of asymptotes. Above a certain value of tube diameter there should be no further increase of induction distance and time with increasing tube diameter. A graph of average detonation induction velocity, that is, the ratio of average induction distance to time, shows that wall effects are noticeable only for tubes with a diameter smaller than about 1 cm. Maximum observed flame velocities, attaining the value of 3.1 km/sec, have been observed immediately following the onset of retonation before the combustion front settles down to the Chapman‐Jouguet detonation with a velocity of 2.8 km/sec. The plot of world lines on the log‐log scale revealed that the development process can be bracketed between two asymptotes, one corresponding to an acceleration which decreases, or is sometimes even negative, and the other with acceleration that increases with time. The average value of observed accelerations was of an order of 106 m/sec2.