Effect of volatiles on ignition delay in coal dust gas suspensions within shock waves

We present the results from an experimental study into the dynamics involved in the formation and the unique features of ignition in shock gas suspensions of coal dust with a dispersion of $<$ 40 $\mu$m and a volatile content of 9, 26, and 55%. We have determined the ignition delays $\tau_{ig}$ for coal dusts in air and in pure oxygen for a range of Mach numbers from 2.6 to 4.0 in an incident shock wave. We have established that the quantity $\tau_{ig}$ as well as the nature of the function $\tau_{ig}(1/T)$ are significantly affected by the kinetics of the volatile yield, in addition to the kinetics of volatile ignition. We have derived an approximation expression for $\tau_{ig}$ as a function of the content of volatiles, the temperature of the medium, and the partial pressure of the oxygen.