INITIATION OF DETONATION REGIMES IN HYBRID 2-PHASE MIXTURES

The problem of detonation initiation is studied in the case of hybrid two-phase mixtures consisting of a hydrogen-air gaseous mixture with s uspended fine aluminium particles. In preceding works on this subject, investigation of the steady propagation regimes has shown that three main propagation regimes could exist: the Pseudo-Gas Detonation (PGD), the Single-Front Detonation (SFD), and the Double-Front Detonation (D FD). In the present study, a one-dimensional unsteady numerical code h as been improved to study the build-up of the detonation in a heteroge neous solid particle gas mixture contained in a tube. The initiation i s simulated by the deposition of a given energy in a point source expl osion, and the formation of the detonation is observed over distances of 15 m to 30 m. As the code has been designed to run on a micro-compu ter, memory limitations preclude sufficient accuracy for quantitative results, however, good qualitative agreement has been found with the r esults of the steady analysis. In addition, it has been demonstrated t hat when both PGD and SFD could exist at the same particle concentrati on, the PGD regime was unstable and was able to exist only over a limi ted distance (a few meters): after some time, the reaction of aluminiu m particles in the unsteady flow perturbs the leading wave and acceler ates it to the SFD regime. Influence of particle diameter and of initi ation energy are examined.