Reseña OctavioRodríguez Araujo(con la colaboración de Gibrán Ramírez Reyes)2012Poder y elecciones en MéxicoMéxico, Orfila208

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Highlights of the Flame Acceleration in a Confined Nonuniform H2/O2/N2 Mixture

International audienceGaseous explosion models generally assume the gas mixture to be uniform. However, in a real explosion, the vapor cloud may not be homogeneous, and repartitioning of the reactivity inside the cloud can be subject to wide spatial variations. In this work, experimental tests were run to study the flame propagation and acceleration in nonuniform mixtures. Experiments were performed in a long vertical confined tube with a square cross section, composed of four equal sections. A gate valve separated the tube into two parts, and the composition of the gases was different on each side of the valve. The opening of the valve permitted the mixing of gases by molecular diffusion. For nonuniform mixtures, a mode of propagation identical to that seen in uniform mixtures was observed; however, a third phase of propagation was found, in which the flame velocity increased strongly. This increase occurred with higher hydrogen concentration in an upwardpropagating flame. A concentration gradient can appreciably modify the trajectory and acceleration of a flame. Here, however, the incidence of pressure effects remained modest, since the combustion was confined and the final pressure depended mainly on the quantity of reactants available

Propagation of Shock Waves in Two Rooms Communicating through an Opening

Confined explosions represent a serious safety hazard as significant damage to humans and structures is observed, unlike in free-field explosions. An experimental small-scale study investigated the blast wave in a single-story building. The blast waves were generated by the detonation of a gaseous charge. The building was divided into two rooms by a movable wall which could be positioned at three different locations. The presence of an opening in this movable wall means that two rooms were considered: a transmitter room (TR) and a receptor room (RR). The configuration without the movable wall was also studied. Pressure profiles recorded with pressure gauges at ground level and on the wall presented numerous reflections. The damage effects were severe since the maximum overpressure never fell below 0.2 bar. Although this study is limited to a small scale and gaseous detonation charge, the results can be applied to a large scale and for a TNT charge

Influence of the geometry of protective barriers on the propagation of shock waves

International audienceThe protection of industrial facilities, classified as hazardous, against accidental or intentional explosions represents a major challenge for the prevention of personal injury and property damage, which also involves social and economic issues. We consider here the use of physical barriers against the effects of these explosions, which include the pressure wave, the projection of fragments and the thermal flash. This approach can be recommended for the control of major industrials risks, but no specific instructions are available for its implementation. The influence of a protective barrier against a detonation-type explosion is studied in small-scale experiments. The effects of overpressure are examined over the entire path of the shock wave across the barrier and in the downstream zone to be protected. Two series of barrier structures are studied. The first series (A) of experiments investigates two types of barrier geometry with dimensions based on NATO recommendations. These recommendations stipulate that the barrier should be 2 m higher than the charge height, the thickness at the crest should be more than 0.5 m, while its length should be equal to twice the protected structure length and the bank slope should be equivalent to the angle of repose of the soil. The second series (B) of experiments investigates the influence of geometrical parameters of the barrier (thickness at the crest and inclination angles of the front and rear faces) on its protective effects. This project leads to an advance in our understanding of the physical phenomena involved in the propagation of blast waves resulting from an external explosion, in the area around a protective physical barrier. The study focuses on the dimensioning of protective barriers against overpressures effects arising from detonation and shows the advantage of using a barrier with a vertical front or rear face

Impact d'une onde de choc sur une structure cylindrique

Dans un contexte de sécurité industrielle, il est important de connaître les caractéristiques de l'onde de souffle consécutive à une explosion d'origine quelconque, lorsque cette explosion se produit à proximité d'un bâtiment, ceci dans le but de protéger les installations et le personnel. Pour cela, une approche expérimentale est envisagée. L'objectif du présent travail est de définir des modèles de chargements appliqués à une structure de forme cylindrique rencontrée dans l'industrie et susceptible de subir une explosion à proximité des murs mais pas à leur contact. Cet objectif est poursuivi de manière originale à travers la réalisation d'essais d'explosions de gaz menés en laboratoire. Un certain nombre de lois sont exprimées et validées par les expériences. Des simulations numériques sont réalisées en parallèle à l'aide du code Autodyn, et une bonne corrélation avec les résultats expérimentaux est obtenue

The Fourth International Symposium on Hazards, Prevention, and Mitigation of Industrial Explosions

International audienc

Direct initiation of gaseous detonation: the Jungle

International audienc

Blast effects: physical properties of shock waves

This book compiles a variety of experimental data on blast waves. The book begins with an introductory chapter and proceeds to the topic of blast wave phenomenology, with a discussion Rankine-Hugoniot equations and the Friedlander equation, used to describe the pressure-time history of a blast wave. Additional topics include arrival time measurement, the initiation of detonation by exploding wires, a discussion of TNT equivalency, and small scale experiments. Gaseous and high explosive detonations are covered as well. The topics and experiments covered were chosen based on the comparison of used scale sizes, from small to large. Each characteristic parameter of blast waves is analyzed and expressed versus scaled distance in terms of energy and mass. Finally, the appendix compiles a number of polynomial laws that will prove indispensable for engineers and researchers