Mechanisms of detonation transmission in layered H2-O2 mixtures

Abstract

Abstract. When a plane detonation propagating through an explosive comes into contact with a bounding explosive, different types of diffraction patterns, which may result in the transmission of a detonation into the bounding mixture, are observed. The nature of these diffraction patterns and the mode of detonation transmission depend on the properties of the primary and bounding explosives. An experimental and analytical study of such diffractions, which are fundamental to many explosive applications, has been conducted in a two channel shock tube, using H2-O2 mixtures of diffi~rent equivalence ratios as the primary and bounding or secondary explosive. The combination of mixtures was varied from rich primary / lean secondary to lean primary / rich secondary since the nature of the diffraction was found to depend on whether the Chapman-Jouguet velocity of the primary mixture, Dp, was greater than or less than that of the secondary mixture, Ds. Schlieren framing photographs of the different diffraction patterns were obtained and used to measure shock and oblique detonation wave angles and velocities for the different diffraction patterns, and these were compared with the results of a steady-state shock-polar solution of the diffraction problem. Two basic types of diffraction and modes of detonation reinitiation were observed. When Dp > Ds, an oblique shock connecting the primary detonation to an oblique detonation in the secondary mixture was observed. With ])p < Ds, two modes of reinitiation were observed. In some cases, ignition occurs behind the Mach reflection of the :shock wave, which is transmitted into the secondary mixture when the primary detonation first comes into contact with it, from the walls of the shock tube. In ether cases, a del:onation is initiated in the secondary mixture when the reflected shock crosses the contact surface behind the incident detonation. These observed modes of Mach stem and contact surface ignition have also been observed in numerical simulations of layered detonation interactions, as has the combined oblique-shock oblique-detonation configuration when Dp > Ds. When Dp > Ds, the primary wave acts like a wedge moving into the secondary mixture with velocity Dp after steady state has been reached, a configuration which also arises in oblique-detonation ramjets and hypervelocity drivers.Correspondence to: Ix[. Tonello

Detonation propagation in hydrogen–air mixtures with transverse concentration gradients

“…Tonello et al [10] investigated layered H 2 -O 2 mixtures experimentally. Similar to the aforementioned studies different types of diffraction patterns were observed depending on the respective reactivities of the primary and secondary mixtures.…”

Gas-phase detonation propagation in mixture composition gradients

“…Some of the initial work in this area was done on the problem of detonation transmission through layers of different gas mixtures [17][18][19]. A detonation was first ignited in one uniform mixture and then allowed to abruptly come into contact with a secondary uniform mixture above or below it (in the direction perpendicular to its direction of propagation).…”

Numerical simulation of dust explosions in pneumatic conveyors

“…As already indicated, this approximation eliminates the need to consider detailed reaction kinetics and the time consuming solution of the governing stiff partial differential equations involved. This approach, which has been successfully used in the numerical calculations of gaseous detonation processes (Tonello 1995), of course, neglects any reactions which occur behind the combustion front.…”