The role of ignition delay time on the deflagration index in a 20l bomb

Deflagration index measurements have been performed in a 20 l sphere for methane/air and methane/nicotinic acid/air mixtures of different compositions at varying ignition delay time and, hence, turbulence level. The severity of explosion increases when nicotinic acid is present; this effect is more pronounced with increasing turbulence level. We then modelled the effect of the initial level of turbulence on the deflagration index values through equations for the turbulent burning velocity as a function of velocity fluctuation. The model well reproduces the experimental data, provided that an adequate equation for the turbulent burning velocity is used.