Critical energy for direct initiation of spherical detonations in H2/N2O/Ar mixtures

Abstract

Although the detonation phenomenon in hydrogen-nitrous oxide mixtures is a significant issue for nuclear waste storage facilities and development of propulsion materials, very limited amount of critical energy data for direct initiation  which provides a direct measure of detonability or sensitivity of an explosive mixture  is available in literature. In this study, the critical energies for direct blast initiation of spherical detonations in hydrogen-nitrous oxide-Ar mixtures obtained from laboratory experiments and theoretical predictions at different initial conditions (i.e., different initial pressure, equivalence ratio and amount of argon dilution) are reported. In the experiments, direct initiation is achieved via a spark discharge from a high voltage and low inductance capacitor and the initiation energy is estimated accordingly from the current output. Characteristic detonation cell sizes of hydrogen-nitrous oxide-Ar mixtures are estimated from chemical kinetics using a recently updated reaction mechanism. A correlation expression is developed as a function of initial pressure, argon dilution and equivalence ratio, which is fitted to provide good estimation of the experimental measured data. The direct link between cell size and critical energy for direct blast initiation is then analyzed. Good agreement is found between experimental results and theoretical predictions, which make use of the cell size estimation correlation and the semi-empirical surface energy model. The effects of the initial pressure, equivalence ratio and the amount of Ar dilution on the critical initiation energy H 2 -N 2 O-Ar mixtures are investigated. By comparing the critical energies with those of H 2 -O 2 -Ar mixtures, it is shown that H 2 -N 2 O mixtures are more detonation sensitive with smaller initiation energies than H 2 -O 2 mixtures at the same initial pressure, equivalence ratio and amount of argon dilution, except for higher diluted condition with amount of argon in the mixture above 20%. Attempt is made to explain the critical energy variation and comparison between the two H 2 -N 2 O-Ar and H 2 -O 2 -Ar mixtures from the induction length analysis and detonation instability consideration.

Adaptive mesh refinement based simulations of three-dimensional detonation combustion in supersonic combustible mixtures with a detailed reaction model

“…Samtaney and Pullin [66] have discussed this problem comprehensively. High-resolution detonation 7 simulations using Euler equations can generate unphysical small-scale features resulted from the low numerical diffusion. Nevertheless, qualitative similarities are observed even in highresolution simulations of viscous and inviscid detonations, especially in regular detonations.…”

“…Except for direct initiation [6][7][8][9] which can realize initiation immediately but need large energy, an alternative is to use a hot jet that can also realize quick initiation [10] . Researches on detonation initiation with a hot jet have been numerously investigated [11][12][13][14][15][16] , but most of them are carried out only in quiescent combustible mixtures.…”

Numerical Investigation on Detonation Control Using a Pulse Hot Jet in Supersonic Combustible Mixture

“…As for initiation method, direct initiation (Zhang et al, 2011a;Zhang et al, 2011b;Zhang et al, 2012;Soury and Mazaheri, 2009) can realize instantaneously detonation formation, but it is not suitable for actual application due to its requirement for large energy.…”

Adaptive simulations of cavity-based detonation in supersonic hydrogen–oxygen mixture

“…Direct initiation [5][6][7] can ignite detonation quickly, but it is not actually applicable due to its necessary usage of large energy. An alternative approach is the utilization of a hot jet which can also ignite detonation initiation very fast [8] , because the flame acceleration process of deflagration to detonation transition (DDT) is bypassed essentially.…”