Correlations for flame speed and explosion overpressure of dust clouds inside industrial enclosures
ABSTRACT Explosion relief vents on enclosures in powder-handling plants are currently designed according to technical standards that in some situations may overestimate the required vent area significantly. These technical standards sometimes do not take into account the real work conditions of industrial plants (e.g. turbulence intensity) and therefore explosion worst cases are not always foreseeable. The availability of methods either for the evaluation of explosion overpressure or sizing of relief vents, with involvement of the pre-ignition turbulence, could be very useful for a better estimate of these quantities. In this work two empirical correlations are presented: the first one allows the calculation of the flame speed and the burning velocity starting from the explosion indices KSt and Pmax of the standardized 20-l sphere test. The second allows either the calculation of the explosion overpressure or the sizing of relief vents of an enclosure.
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ABSTRACT: We conducted experiments to examine the explosion characteristics of different sizes of micro-sized and nano-sized magnesium dust. These explosion characteristics, such as the maximum explosion pressure and maximum rate of pressure rise, depend on the dust concentration. Changes in the particle sizes do not cause clear differences in the explosion characteristics of nano-sized magnesium dust. However, the explosion characteristic values of micro-sized magnesium dust decrease with increasing particle size. Furthermore, nano-sized magnesium dust showed greater explosion characteristics than micro-sized magnesium dust. The calculated flame propagation velocity showed the same trend as the maximum explosion pressure and maximum rate of the pressure rise. The results of classifying the explosion intensity hazards of a magnesium dust explosion showed that the explosion index increased with the decrease of particle size.Journal of Korean Society of Hazard Mitigation. 01/2013; 13(2).
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ABSTRACT: The on-way peak overpressure and flame propagation speed of gas deflagration in the tube with obstacles are important data for process safety. Based on carbon monoxide deflagration experiments, the paper presents a multi-zone integration model for calculation of on-way peak overpressure, in which the tube with obstacles is considered as a series of venting explosion enclosures which link each others. The analysis of experimental data indicates that the on-way peak overpressure of gas deflagration can be correlated as an empirical formula with equivalence ratio of carbon monoxide oxidation, expansion ratio, flame path length, etc., and that the on-way peak overpressure exhibits a linear relationship with turbulence factor and flame propagation speed. An empirical formula of flame propagation speed is given.Science China Technological Sciences 53(7). · 1.19 Impact Factor
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ABSTRACT: This paper presents the results of experimental investigation on characteristics of methane-coal dust mixture explosion and its mitigation by ultra-fine water mist. Four E12-1-K type fast response thermocouples, two PCB piezotronic pressure transducers were used to obtain the temperature and pressure history of methane-coal dust mixture explosion and its mitigation by ultra-fine water mist, while a GigaView High-speed camera was used to visualize the processes. Different methane concentrations, coal dust concentrations, diameters of coal particles and volumes of ultra-fine water mist were considered for their effects on methane-coal dust mixture explosion. The temperature of explosion flame, the maximum explosion overpressure, the maximum rate of overpressure rise, and the critical volume flux of ultra-fine water mist were experimentally determined. The results show that the characteristics of the methane-coal dust mixture explosion and the mitigating efficiency by ultra-fine water mist are influenced by the methane concentration, the coal dust concentration, the coal dust diameter and the applied volume flux of ultra-fine water mist. For example, both the maximum explosion overpressure and rate of overpressure rise increased with increasing of coal dust concentrations and methane concentrations. All of the test cases indicate that ultra-fine water mist can mitigate the mixture explosion and suppress the flame propagation efficiently from the images record by high speed video camera.Journal of Engineering for Gas Turbines and Power 01/2012; 134(6):061401-061406. · 0.82 Impact Factor