Flame self-sustaining

Therefore, if a large quantity of sample is introduced into the flame over a short period of time, the flame temperature will fall, thus interfering with the basic processes leading to the formation and operation of the plasma. Consequently introduction of samples into a plasma flame needs to be controlled, and there is a need for special sample-introduction techniques to deal with different kinds of samples. The major problem with introducing material other than argon into the plasma flame is that the additives can interfere with the process of electron formation, a basic factor in keeping the flame self-sustaining. If electrons are removed from the plasma by... 

The autoignition temperature is the minimum temperature required for self-sustained combustion in the absence of an external ignition source. The value depends on specified test conditions. Tht flammable (explosive) limits specify the range of concentration of the vapor in air (in percent by volume) for which a flame can propagate. Below the lower flammable limit, the gas mixture is too lean to burn above the flammable limit, the mixture is too rich. Additional compounds can be found in National Fire Protection Association, National Fire Protection Handbook, 14th ed., 1991. 

The ignition temperature or autoignition temperature is the minimum temperature of a flammable mixture that is required to initiate or cause self-sustained combustion without ignition from an external source of energy such as a spark or flame (ASTM D2155). 

Flammability Limits There are both upper (or rich) and lower (or lean) limits of flammability of fuel-air or fuel-oxygen mixtures. Outside these hmits, a self-sustaining flame cannot form. Flammability limits for common fuels are listea in Table 27-18. 

The preceding section described the state of transition expected in a deflagration process when the mixture in front of the flame is sufficiently preconditioned by a combination of compression effects and local quenching by turbulent mixing. However, additional factors determine whether the onset of detonation can actually occur and whether the onset of detonation will be followed by a self-sustaining detonation wave. 

A flame is a thin region of rapid, self sustaining oxidation of fuel that is often accompanied by the release of large amounts of heat and light. Flames are what we most coninionly associate with combustion. One part of combustion science focuses on the different ways flames can be formed and the scientific and practical consequences of each. 

Auloignition lempemlure The lowest temperature of a material required to initiate or cause self-sustained combustion in the absence of a spark or flame. This temperature can vary, depending on the substance, its size, and the shape of the igniting surface or container and other factors [32]. 

D. Durox, T. Schuller, and S. Gandel. Self-sustained oscillations of a premixed impinging jet flame on a plate. Proc. Combust. Inst., 29 69-75, 2002. 

Substances applied to or incorporated in a combustible material (e.g. organic polymers, nylon, vinyl and rubber, etc.) to reduce flammability. Act by retarding ignition, control/douse burning, reduce smoke evolution. Slow down or interrupt the self-sustained combustion cycle when the heat-flux is limited. Flame retardants (FRs) improve the combustion behaviour and alter the combustion process (cool, shield, dilute, react) so that decomposition products will differ from nonflame retarded articles. FRs are usually divided into three classes ... 

The burning mechanism of composite propellants differs from that described above. There is no exothermic reaction which can lead to a self-sustaining fizz zone. Instead, the first process appears to be the softening and breakdown of the organic binder/fuel which surrounds the ammonium perchlorate particles. Particles of propellant become detached and enter the flame. The binder is pyrolysed and the ammonium perchlorate broken down, initially to ammonia and perchloric acid. The main chemical reaction is thus in the gas phase, between the initial dissociation products. 

Hot Flame Ignition - A rapid self-sustaining, sometimes audible gas phase reaction of the sample or its decomposition products with an oxidant. A readily visible yellow or blue flame usually accompanies the reaction. 

For those who have not studied fluid mechanics, the definition of a deflagration as a subsonic wave supported by combustion may sound over sophisticated nevertheless, it is the only precise definition. Others describe flames in a more relative context. A flame can be considered a rapid, self-sustaining chemical reaction occurring in a discrete reaction zone. Reactants may be introduced into this reaction zone, or the reaction zone may move into the reactants, depending on whether the unbumed gas velocity is greater than or less than the flame (deflagration) velocity. 

---