Gas cloud explosion — Current status

Abstract

Some recent progress in gas explosion research is summarized in this paper. Turbulence created by spatially distributed large obstructions in the path of the flame is established to be the most important flame acceleration mechanism giving rise to extremely violent deflagrations. A decrease in the degree of confinement, however, as well as departure from stoichiometry in the mixture composition, has significant influence on suppressing this powerful flame acceleration mechanism by limiting the magnitude of the displacement flow velocity. A typical maximum turbulent flame speed is observed to be of the order of 800 m/s and is attained when the dual role played by turbulence in quenching and augmentation of chemical reactions, comes to an equilibrium. A turbulent jet of hot products is found to be an important strong ignition source which may lead to very high burning rates and even initiation of detonation. Quenching may result, however, when the cooling from the adiabatic expansion of an underexpanded supersonic jet and further turbulent mixing have reduced the temperature to below the ignition value. Important recent progress in fuel-air detonation is mainly due to the ability to link the cell size of the detonation to the various dynamic detonation parameters. When these correlations have been confirmed by further experiments, future efforts in the study of fuel-air detonations may be reduced to simple measurements of detonation cell size. Initiation requirements and detonability limits can then be deduced from the cell size information.