Effect of temperature on the concentration explosion limits of combustible liquids (original) (raw)
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A thermal theory for estimating the flammability limits of a mixture
Fire Safety Journal, 2011
Because it is difficult to treat the contributions of diluents explicitly using Le Chatelier's rule, a methodology based on thermal balance is proposed for estimating the flammability limits of a mixture. This method converts the flammability information of a mixture into a binary domain of heating/ quenching potentials and, after some simple manipulations, converts them back into the flammability domain. The advantage of this conversion is the separation of the heating and quenching potential sums. The dual contribution (heating and quenching) of each species is stressed, while the simplicity of hand calculation is preserved. This method is equivalent to Le Chatelier's rule but has increased flexibility in dealing with various fuel/oxygen/diluents combinations. It will help safety engineers gain more confidence in the hazard analysis of flammable mixtures involving diluents.
Dependence of the lower flammability limit on the initial temperature
Combustion, Explosion, and Shock Waves, 2012
The dependence of the lower flammability limit on the initial temperature is studied experimentally and numerically for upward flame propagation at a pressure of 0.1 MPa. It is shown that the Burgess and Wheeler rule, implying a linear dependence of the lower flammability limit on the initial temperature with the intersection of the temperature axis at the point 1300 • C, does not hold for N 2 , CH 3 OH, CH 2 O, and CH 4. For these substances, the intersection of the temperature axis is at the point 900 ± 20 • C. The Burgess and Wheeler rule gives overestimated values of the limit which do not reflect the true conditions of explosion safety.
Journal of Chemical & Engineering Data, 2010
The lower flammability limits of 18 C x H y O z N w liquids were measured as a function of initial temperature in an ASHRAE 12 L style apparatus. Results indicate that the calculated adiabatic flame temperature is not constant, as previously reported but rather decreases with increasing temperature. Consequently, the modified Burgess-Wheeler law does not accurately predict the effect of temperature on the lower flammability limit. Though few direct comparisons are possible, previously reported data agree well with the values measured in this study.
CALCULATION OF FLASH POINTS AND FLAMMABILITY LIMITS OF SUBSTANCES AND MIXTURES
Flash point and flammability limits are important factors in the development of safe practices for handling and storage of pure substances and mixtures. Regulatory authorities use data for flash point in order to classify flammable and combustible substances. In the proposed work a critical evaluation of the methods for calculation of flash point and flammability limits of individual substances and liquid mixtures was made.
Experimental determination of the lower explosion limit for two gasoline samples
MATEC Web of Conferences
The explosive atmosphere may be caused by flammable gases / vapours or combustible dust. If the amount of the substance, mixed with air, is sufficient, then a source of ignition is needed to cause an explosion. Liquids (for example petrol and other fuels) and solvents from industrial products emit flammable vapours which, when mixed with air, can ignite or explode. At normal temperatures, flammable liquids can emit enough vapours to form combustible mixtures with air, heat, and often thick, black, and toxic clouds of smoke. The behaviour of a fuel-oxidant mixture is characterized by certain explosions parameters, including explosion limits, which characterize the range of concentrations in which combustion propagates at very high speeds. For this work were performed experimental determination of the lower explosion limit for two commercial gasoline samples.
2017
This work defines density factor as the ratio of before ignition density to after ignition density of the ignition mixture. This work provides an estimation method for explosive limits of various fuels under room temperature and pressure by showing that for a large universe of fuels, constant adiabatic flame temperature and density factor are appropriate approximations at the lower explosive limit while only a constant density factor might be an appropriate approximation at the upper explosive limit. Thus the assumption of a constant adiabatic flame temperature can be used in calculating lower explosive limit while the assumption of a constant density factor can be used in approximating upper explosive limit.
Effects of hydraulic resistance and heat losses on detonability and flammability limits
Combustion Theory and Modelling, 2004
This paper presents an analysis of a one-dimensional combustion model capable of describing both deflagrations and detonations. Incorporating volumetric terms to account for hydraulic and thermal losses, the quenching diameters, below which each type of combustion wave cannot propagate, are calculated. The main conclusion is that, as expected, detonations have larger quenching diameters than deflagrations for sufficiently high activation energies. However, the opposite result is found for relatively low activation energies.
Journal of Hazardous Materials, 2006
Detonation temperature of C a H b N c O d explosives can be predicted from a, b, c, d and calculated gas phase heat of formation of explosives without using any assumed detonation products and experimental data. Two new correlations are introduced for calculation of detonation temperature of aromatic and non-aromatic explosive compounds so that it is shown here how simply calculated heat of formation by additivity rule and atomic composition are only necessary data for this simple prediction. Calculated detonation temperatures by the introduced correlations for both pure and explosive formulations show good agreement with respect to measured detonation temperatures and complicated computer codes. The average mean absolute error in detonation temperature is within about 7.0%.
Flammability of gas mixturesPart 1: Fire potential
Journal of Hazardous Materials, 2005
International and European dangerous substances and dangerous goods regulations refer to the standard ISO 10156 (1996). This standard includes a test method and a calculation procedure for the determination of the flammability of gases and gas mixtures in air. The substance indices for the calculation, the so called "Tci values", which characterise the fire potential, are provided as well. These ISO Tci values are derived from explosion diagrams of older literature sources which do not take into account the test method and the test apparatus. However, since the explosion limits are influenced by apparatus parameters, the Tci values and lower explosion limits, given by the ISO tables, are inconsistent with those measured according to the test method of the same standard. In consequence, applying the ISO Tci values can result in wrong classifications. In this paper internationally accepted explosion limit test methods were evaluated and Tci values were derived from explosion diagrams. Therefore, an "open vessel" method with flame propagation criterion was favoured. These values were compared with the Tci values listed in ISO 10156. In most cases, significant deviations were found. A detailed study about the influence of inert gases on flammability is the objective of Part 2.