Combustible gases autoignition

Cinefilms of knocking combustion by Withrow and Rassweiler [49] showed, as early as 1936, that in a knocking cycle the end gas autoignites... 

Although the onset of end gas autoignition is influenced primarily by the autoignition chemistry in the end gas, it is also affected by the speed with which the flame propagates across the combustion volume. This is because the pressure and temperature of the end gas depend, not only... 

This section discusses the problems of combining models of engine combustion and of end gas autoignition. But prior to this, some effects observed in engines which complicate this endeavour, involving the carryover of reactive species from one cycle to another, are diseussed. 

BROMOMETHANE (74-83-9) CHjBr Combustible gas, but not easily ignited it has narrow flammability limits in air [explosion limits in air (vol %) 10 to 16 autoignition temp 999 F/537°C Fire Rating 1]. The sensitivity of these limits may be widened by pressure contact with oxygen, aluminum. 

Combustion of a flammable gas-air mixture occurs if the composition of the mixture lies in the flammable range and if there is a source of ignition. Alternatively, combustion of the mixture occurs without a source of ignition if the mixture is heated up to its autoignition temperature. 

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. 

Undesirable combustible gases and vapors can be destroyed by heating to the autoignition temperature in the presence of sufficient oxygen to ensure complete oxidation to CO2 and H2O. Gas incinerators are appHed to streams that are high energy, eg, pentane, or are too dilute to support combustion by themselves. The gas composition is limited typicaUy to 25% or less of the lower explosive limit. Gases that are sufficiendy concentrated to support... 

The niaxiinwn spontaneous ignition temperature (SIT) or autoignition temperature (AIT) is defined as die minimum temperature at wliicli combustion occurs in a bulk gas mixture when die temperature of a flaiiunable gas-air mixture is raised in a unifonidy heated apparatus. The autoignidon temperature represents... 

When pressure-decay rates less than critical are employed, the gas-phase combustion zone is removed from the propellant surface and extinguished, but not the ignition from within the condensed phase. Therefore, the temperature of the surface material will be above the autoignition temperature, and steady-state combustion will eventually be initiated. This mechanism is consistent with the observation that the luminosity of the combustion zone can vanish without combustion having been completely terminated. 

A third approach has been suggested by Jaroudi (Jl), who points out that one necessary condition to prevent reignition of the propellant is to ensure that the gas temperature resulting from thermal equilibrium between the injected fluid and the combustion products is below the propellant autoignition temperature. This approach leads to the conclusion that the ratio of coolant mass flow to propellant mass flow is the critical correlating parameter. 

Enhanced oil-recovery processes include chemical and gas floods, steam, combustion, and electric heating. Gas floods, including immiscible and miscible processes, are usually defined by injected fluids (carbon dioxide, flue gas, nitrogen, or hydrocarbon). Steam projects involve cyclic steam (huff and puff) or steam drive. Combustion technologies can be subdivided into those that autoignite and those that require a heat source at injectors [521]. 

It may ignite in air [1], particularly if air is admitted suddenly into the gas at reduced pressure [2], Although digermane and its homologues do not usually ignite on exposure to air, their autoignition temperatures appear to be about 50°C and combustion is rapid or explosive [3],... 

White phosphorus has an autoignition temperature only shghtly above ambient, dispersed it will soon heat itself to that by the slow oxidation responsible for its glow. Red is not spontaneously combustible, however if it does catch fire white will be produced, so that the fire, once extinguished, may spontaneously re-ignite. Both can produce phosphine, among other products, by slow reaction with water. Sealed containers of damp phosphorus (white is often stored under water) may pressurise with highly toxic, pyrophoric, gas mixtures [1]. 

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