ABSTRACT
Ignition is a process during which combustible mixtures begin to burn. An explosion occurs during a short timescale (t), or also within a short distance,
d (
d
=
v * t) as
a wave
. It could be in the form of a temperature explosion (a useful criterion in flow systems) or a pressure explosion (a useful criterion in rigid systems). Ignition is an explosive process in which T rises rapidly for an open system or T and P rise rapidly for a closed system. Autoignition is the process of initiating ignition using a hotter ambient without using an ignition source such as a spark or a flame from a matchstick. Ignition is of great importance for a number of different practical situations: spontaneous combustion in stocked coal, ignition of dust clouds leading to explosive propagation in coal grinding and conveying equipment, and ignition in a pulverized-coal flame. The basic essentials of ignition are: (1) fuel, (2) oxidizer, (3) heat, and (4) reaction kinetics called the
fire tetrahedron
in which sufficient heat must be generated or a minimum temperature achieved to sustain combustion.
