Prediction model for self-similar propagation and blast wave generation of premixed flames

This paper presents a simple model to predict the flame speed and the blast pressure during an unconfined gas explosion. The proposed model is a modification to the fractal-based model proposed by Gostintsev et al. In the original model, the flame radius, r, is expressed as a function of time, t, as r/(κ/εSL)=cg[t/(κ/ε2SL2)]α, where κ is the thermal diffusivity, ε is the volumetric expansion ratio, SL is the laminar burning velocity, cg is the model constant, and α is the acceleration exponent. The present model expresses model constant cg using the properties of gas mixture. In this study, field experiments of gas explosion are conducted for hydrogen/air, methane/air, and propane/air mixtures confined in a 1- or 27-m3 regular cubic plastic tent. The experimental results demonstrate the nature of self-similarity in the explosions and the experimental acceleration exponent associated with a fractal dimension is evaluated. The model is developed by using the concept of self-similarity and an acoustic theory. The predicted flame speed and the blast pressure are compared with experimental data of larger-scale hydrogen/air, methane/air and propane/air explosions under a wide range of conditions. The model predictions agree reasonably well with the experimental data, validating the proposed model.