Ignition energy definition

The fundamental parameters in the two main methods of achieving ignition are basically the same. Recent advances in the field of combustion have been in the development of mathematical definitions for some of these parameters. For instance, consider the case of ignition achieved by means of an electric spark, where electrical energy released between electrodes results in the formation of a plasma in which the ionized gas acts as a conductor of electricity. The electrical energy Hberated by the spark is given by equation 2 (1), where V = the potential, V 7 = the current. A 0 = the spark duration, s and t = time, s. 

A combustion process is an exothermic reaction initiated by a source of ignition that produces more energy than it consumes. The speed at which the reaction proceeds through the mixture of reactants depends on the concentration of the flammable gas or vapor. This speed is lower at higher ( rich ) as well as a lower ( lean ) concentrations of the flammable gas than at the stoichiometric mixture. There are lower and upper limits beyond which the reaction cannot propagate through the gas mixture on its own. Some definitions follow ... 

Ignition processes often are characterized by a gradual increase of temperature that is followed by a rapid increase over a very short time period. This behavior is exhibited in the present problem if a nondimensional measure of the activation energy E is large, as is true in the applications. Let tc denote an ignition time, the time at which the rapid temperature increase occurs a more precise definition of arises in the course of the development. In the present problem, during most of the time that t < tc, the material experiences only inert heat conduction because the heat-release term is exponentially small in the large parameter that measures E. The inert problem, with w = 0, has a known solution that can be derived by Laplace transforms, for example, and that can be written as... 

Enclosure Housings for Classified Environments. Only electrical apparatus which meet the requirements of being intrinsically safe (IS) are allowed to be located in potentially explosive environments without protective enclosures. Intrinsically safe devices are by definition those whose electrical and thermal energy are limited, under both normal and abnormal conditions, to be below the ignition conditions of the hazardous mixture... 

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