Numerical simulation of modes of combustion and detonation of hydrogen-air mixtures in porous medium in the framework of the mechanics of two-phase reaction mediums

Abstract

Numerical simulation is carried out for combustion and detonation waves propagating through a motionless gas mixture in a porous inert charge. Computations are performed in a one-dimensional approximation by means of an EFAE computer program that was developed in the framework of the mechanics of multiphase reaction mediums. The chemical conversion of gas is modeled by a one-stage reaction of the Arrhenius type with constants selected based on existing experimental data on the ignition lags behind the reflected shock waves. Computations are performed for hydrogen-air mixtures with 35 and 15% hydrogen and compared with literature experimental data in which the initial pressure and the diameter of charged particles are varied. All three combustion modes (slow, fast, and supersonic) observed in the experiment and combustion failure under conditions lower than threshold are followed by numerical simulation. In addition, the computations qualitatively reproduced experimental data on the change of the combustion mode in the case of transfer from stoichiometric to a lean mixture and data on the combustion wave velocity and limiting conditions of combustion mode transition and failure of flame as a function of the initial pressure and the charged particle size. It is shown that supersonic waves propagating with a velocity of lower than 1100 m/s do not have a Chapman-Jouguet surface in the end of the reaction zone and it is evident that they can be related to detonation, as in the cited literature.