Flammability limits of complex

A calculation of the flammability limits of complex gas mixtures is carried out by the application of the mixture rule. Stated simply, the mixture rule is that if two limit mixUires of different gases are added together, the resulting mixmre also will be a limit mixture. The mathematical statement of this law is as follows ... 

It is necessary, in approaching most problems to obtain the limits of flammability of the particular gas mixture in question. Few industrial fuel gases are composed of pure gases or vapors, but are mixtures in most cases of many different gases. If the equipment and time are available, a number of mixtures of die fuel gas-air mixtures may be prepared and their flammabilities tested by ignition but it is much easier to determine the flammability limits of complex gas mixtures by calculation. Experience has shown that the results obtained are sufficiently dependable. 

The complex and incompletely understood phenomena of cool flames and then-close relationship with autoignition processes is discussed in considerable detail. As the temperature of mixtures of organic vapours with air is raised, the rate of autoxidation (hydroperoxide formation) will increase, and some substances under some circumstances of heating rate, concentration and pressure will generate cool flames at up to 200° C or more below their normally determined AIT. Cool flames (peroxide decomposition processes) are normally only visible in the dark, are of low temperature and not in themselves hazardous. However, quite small changes in thermal flux, pressure, or composition may cause transition to hot flame conditions, usually after some delay, and normal ignition will then occur if the composition of the mixture is within the flammable limits. 

Well water was routinely used within this chemical complex. This lesson was so unique because it involved such fundamentals as gas density, flammable limits, and sample point orientation. The company held a series of meetings and shared their recommendations with over 800 maintenance and operations employees, engineers, and supervisors. 

Flame stability is governed by the limits of flammability and ignition temperature of the fired fuel. Due to the complex chemistry it is generally impractical to predict precisely using CFD modeling. Scale tests and actual field data are used to extend simple ID and 2D models for calibration to predict flame stability. The variables... 

M. G. Zabetakis and J. K. Richmond, The Determination and Graphic Representation of the Limits of Flammability of Complex Hydrocarbon Fuels at Low Temperatures and Pressures, in Fourth Symposium (Internat.) on Combustion, Williams Wilkins Co., Baltimore, 1953, pp. 121-126. 

The inhibition chemistry of essentially rich hydrocarbon flames with equivalence ratio close to the flammability limit is not adequately investigated. It is explained by very complex combustion chemistry of soot and its precursors formation, which interaction with inhibitor was not explored. 

Typically, the dimensionless group x will involve the concentration of the reactant uq and will increase as ao decreases. This gives rise to a flammability limit . For ao sufficiently small, i.e., for a mixture that becomes too lean in A, X exceeds Xcr and a flame cannot be initiated. For more complex reactions involving both fuel and oxidant, the appropriate concentration will usually be that of the component in which the system is stoichiometrically deficient - allowing two flammability. limits, one appropriate to becoming lean in fuel, the other in the oxidant. 

Needs high vacuum for best performance Difficult to apply to complex geometries Upper temperature limit of 425-475 K Application skill required for best performance Flammable... 

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