Ignition Theory: Application to the Design of New Ignition Systems

Abstract

A theory Is presented on the ignition of solid compositions. The effect of certain physical, chemical and themal properties of a solid cooposition on the ignition time and ignition energy is explained and supported by experimental evidence. Different types of ignition systems are described. Problem areas of the normal ignition systoms are discussed and a technique to overcome these problem areas is offered. By use of the developed ignition theory and a hot-bath immersion test apparatus, a technique of determining the true ignition temperature of a conposition is described. flow, qin^, will be assumed.

Review of Gasless Pyrotechnic Time Delays

“…Ignition of a bulk sample. The critical ignition temperature, T ign , is the minimum temperature to which a pyrotechnic charge of specified size, shape and boundary constraints must be heated in order to induce a thermal runaway [58]. Figure 4 shows a schematic plot of the heat generated versus heat loss as a function of temperature.…”

“…The simplest model for ignition assumes that the ignition temperature, T ign , is a constant for a given composition [58]. It is taken as that temperature to which composition must be heated for it to ignite and combust without further energy input from external source.…”

“…It is taken as that temperature to which composition must be heated for it to ignite and combust without further energy input from external source. The most rudimentary model ignores reagent conversion [58]. This simplifies the governing differential equation to transient heat conduction into a semi-infinite slab subjected to a constant heat flux entering at the ignition end of the column.…”

“…The ignition time is estimated by calculating the time necessary for the outer surface to reach T ign . This approach yielded the following expressions for the ignition time for a sample subjected to a constant incident heat flux [58]:…”