Influences of Turbulence and Combustion Regimes on Explosions of Gas-dust Hydrid Mixtures

Influences of Turbulence and Combustion Regimes on Explosions of Gas-dust Hydrid Mixtures
Author: Nicolas Cuervo Rodriguez
Publisher:
Total Pages: 0
Release: 2015
Genre:
ISBN:

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Predicting the flame propagation during a dust/gas hybrid mixture explosion in complex geometries is a challenge that mobilizes numerous resources. One approach consists on experimentally determining the inherent characteristics of dust-air mixtures, like the laminar flame speed, and using them as input for Computational Fluid Dynamics (CFD) simulation programs. Nevertheless, the experimental characterization of the burning rates of turbulent dust clouds in air still delicate due to the variability of the properties of powders (particle size distribution, moisture...), the physical impossibility to generate a quiescent dust cloud and the impact of powder on the flame radiation among others. The ultimate goal of this work was to develop an approach to assess fundamental flame propagation properties, from closed vessel experiments and pressure-time evolution curves, but specially from the analysis of flame velocity as a function of its stretching and of the hydrodynamic instabilities. In a first step, the turbulence of the initial dust cloud has been studied. The impact of the pyrolysis phase on organic dusts explosion has also been highlighted both experimentally and by means of model for flash pyrolysis. Furthermore, the explosive behaviour of gas-dusts hybrid mixtures composed of pyrolysis gases and organic dusts has been analysed. Finally, the turbulence/combustion interactions during flame propagation have been studied in order to extract the “pseudo” laminar flame velocity of dusts clouds or hybrid mixtures.

Gas, Dust and Hybrid Explosions

Gas, Dust and Hybrid Explosions
Author: W.E. Baker
Publisher: Elsevier
Total Pages: 277
Release: 2012-12-02
Genre: Technology & Engineering
ISBN: 044459809X

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Damaging accidental explosions are a continuous threat to industry. Categories for such explosions include combustible dust explosions; reactive gas explosions, both confined and unconfined; hybrid explosions involving both gases and dusts; bursts of pressure vessels and piping; and liquid propellant explosions. This book evaluates the physical processes and resulting blast effects for these types of explosions. Special attention is given to reactive gas explosions, both confined and unconfined. This latter class of explosion has occurred all too frequently in refineries and petrochemical complexes, and is also one of the most difficult to predict and evaluate. Much recent work on this topic is reviewed and summarized. This is the only publication of its kind, to date, that offers such a thorough coverage of these types of industrial explosions. [p] Each class of explosion source is reviewed separately, first discussing fundamentals, then presenting methods of analysis and testing, and finally giving curves or equations to predict effects of the particular class of explosion. An extensive bibliography is included together with tables of pertinent properties of explosive materials. The text also includes many figures, equations, tables and a keyword index. The book is intended for researchers in the field of characterizing and mitigating industrial explosions. It will also be of interest to engineers, scientists, and insurers involved in processes.

Gaseous Detonations

Gaseous Detonations
Author: M.A. Nettleton
Publisher: Springer Science & Business Media
Total Pages: 266
Release: 2012-12-06
Genre: Medical
ISBN: 9400931492

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My introduction to the fascinating phenomena associated with detonation waves came through appointments as an external fellow at the Department of Physics, University College of Wales, and at the Department of Mechanical Engineering, University of Leeds. Very special thanks for his accurate guidance through the large body of information on gaseous detonations are due to Professor D. H. Edwards of University College of Wales. Indeed, the onerous task of concisely enumerating the key features of unidimensional theories of detonations was undertaken by him, and Chapter 2 is based on his initial draft. When the text strays to the use of we, it is a deserved acknow ledgement of his contribution. Again, I should like to thank Professor D. Bradley of Leeds University for his enthusiastic encouragement of my efforts at developing a model of the composition limits of detonability through a relationship between run-up distance and composition of the mixture. The text has been prepared in the context of these fellowships, and I am grateful to the Central Electricity Generating Board for its permission to accept these appointments.

Investigation of Explosion Characteristics of Multiphase Fuel Mixtures with Air

Investigation of Explosion Characteristics of Multiphase Fuel Mixtures with Air
Author: Emmanuel Kwasi Addai
Publisher: Western Engineering, Inc.
Total Pages: 265
Release: 2016-10-10
Genre: Science
ISBN: 0991378229

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Explosion hazards involving mixtures of different states of aggregation continue to occur in facilities where dusts, gases or solvents are handled or processed. In order to prevent or mitigate the risk associated with these mixtures, more knowledge of the explosion behavior of hybrid mixtures is required. The aim of this study is to undertake an extensive investigation on the explosion phenomenon of hybrid mixtures to obtain insight into the driving mechanisms and the explosion features affecting the course of hybrid mixture explosions. This was accomplished by performing an extensive experimental and theoretical investigation on the various explosion parameters such as: minimum ignition temperature, minimum ignition energy, limiting oxygen concentration, lower explosion limits and explosion severity. Mixtures of twenty combustible dusts ranging from food substances, metals, plastics, natural products, fuels and artificial materials; three gases; and six solvents were used to carry out this study. Three different standard equipments: the 20-liter sphere (for testing lower explosion limits, limiting oxygen concentration and explosion severity), the modified Hartmann apparatus (for testing minimum ignition energy) and the modified Godbert–Greenwald (GG) furnace (for testing minimum ignition temperature) were used. The test protocols were in accordance with the European standard procedures for dust testing for each parameter. However, modifications were made on each equipment in order to test the explosion properties of gases, solvents, and hybrid mixtures. The experimental results demonstrated a significant decrease of the minimum ignition temperature, minimum ignition energy and limiting oxygen concentration of gas or solvent and increase in the likelihood of explosion when a small amount of dust, which was either below the minimum explosion concentration or not ignitable by itself, was mixed with gas or solvent and vice versa. For example, methane with minimum ignition temperature of 600 °C decreased to 530 °C when 30 g/m3 of toner dust, which is 50 % below its minimum explosible concentration was, added. A similar explosion behavior was observed for minimum ignition energy and limiting oxygen concentration. Furthermore, it was generally observed that the addition of a non-explosible concentration of flammable gas or spray to a dust-air mixture increases the maximum explosion pressure to some extent and significantly increases the maximum rate of pressure rise of the dust mixture, even though the added concentrations of gases or vapor are below its lower explosion limit. Finally, it could be said that, one cannot rely on the explosion properties of a single substance to ensure full protection of an equipment or a process if substances with different states of aggregate are present.

Dust Explosions

Dust Explosions
Author:
Publisher: Academic Press
Total Pages: 328
Release: 2019-07-05
Genre: Technology & Engineering
ISBN: 0128175516

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Methods in Chemical Process Safety, Volume Three, addresses the most important challenges, recent advancements and contributions in chemical process safety. The work helps researchers and professionals obtain guidance on the selection and practice of chemical process safety methods. Chapters in the book cover Experimental Methods, Hazard Identification, Risk Assessment, Safety Measures, Regulations, Guidelines and Standards, Emerging/Unique Scenarios, and more. Users will find a complete guide that presents tactics in process safety management that are now globally recognized as the primary approach for establishing a high level of safety in operations. As process safety is now a disciplined framework for managing the integrity of operating systems and processes handling hazardous substances, and because continued occurrence of major losses have had a significant impact on the industry’s approaches to modern process safety, this book is a must have for those in the industry. Acquaints the reader/researcher with the fundamentals of process safety Provides the most recent advancements and contributions in each topic from a practical point-of-view Gives readers the views/opinions of experts on each topic

Gasdynamics of Explosions and Reactive Systems

Gasdynamics of Explosions and Reactive Systems
Author: A. K. Oppenheim
Publisher: Elsevier
Total Pages: 787
Release: 2013-10-22
Genre: Science
ISBN: 1483150054

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Gas Dynamics of Explosions and Reactive Systems documents the proceedings of the 6th Colloquium held at the Royal Institute of Technology in Stockholm, Sweden, 22-26 August 1977. The meeting was held under the auspices of the Royal Swedish Academy of Sciences and the International Academy of Astronautics. The scientific program included over one hundred papers. The contributions in this volume are organized into four parts. Part I contains papers on gaseous detonations. It covers topics such as theoretical model of a detonation cell; spherical detonations in hydrocarbon-air mixtures; and shock wave propagation in tubes filled with water foams. Part II presents studies on explosions, such as the detonation of hydrogen azide and propagation of a laser-supported detonation wave. Part III examines condensed phase detonations. It includes papers on the mechanism of the divergent and convergent dark waves originating at the charge boundary in detonating liquid homogeneous explosives with unstable detonation front; and initiation studies in sensitized nitromethane. Part IV presents discussions on turbulent detonations, covering topics such as the computational aspects of turbulent combustion and problems and techniques in turbulent reactive systems.

Coal Abstracts

Coal Abstracts
Author:
Publisher:
Total Pages: 752
Release: 1986
Genre: Coal
ISBN:

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Turbulent Combustion in SDF Explosions

Turbulent Combustion in SDF Explosions
Author:
Publisher:
Total Pages: 26
Release: 2009
Genre:
ISBN:

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A heterogeneous continuum model is proposed to describe the dispersion and combustion of an aluminum particle cloud in an explosion. It combines the gas-dynamic conservation laws for the gas phase with a continuum model for the dispersed phase, as formulated by Nigmatulin. Inter-phase mass, momentum and energy exchange are prescribed by phenomenological models. It incorporates a combustion model based on the mass conservation laws for fuel, air and products; source/sink terms are treated in the fast-chemistry limit appropriate for such gasdynamic fields, along with a model for mass transfer from the particle phase to the gas. The model takes into account both the afterburning of the detonation products of the C-4 booster with air, and the combustion of the Al particles with air. The model equations were integrated by high-order Godunov schemes for both the gas and particle phases. Numerical simulations of the explosion fields from 1.5-g Shock-Dispersed-Fuel (SDF) charge in a 6.6 liter calorimeter were used to validate the combustion model. Then the model was applied to 10-kg Al-SDF explosions in a an unconfined height-of-burst explosion. Computed pressure histories are compared with measured waveforms. Differences are caused by physical-chemical kinetic effects of particle combustion which induce ignition delays in the initial reactive blast wave and quenching of reactions at late times. Current simulations give initial insights into such modeling issues.