Run-Up Distance From Deflagration to Detonation In Fast Flames PDF Download
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Author: Mohamed Saifelislam Abdelgadir Ahmed
Publisher:
ISBN:
Category : University of Ottawa theses
Languages : en
Pages :
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Book Description
In the process of deflagration-to-detonation transition (DDT) in reactive gases, the flame typically accelerates first to the choked flame condition (known as a Chapman-Jouguet deflagration), where it propagates at the sound speed with respect to the product gases. Subsequently, the choked flame may transit to a detonation. In the present study, the transition length from choked flames to detonations was measured experimentally in laboratory-scale experiments in methane, ethane, ethylene, acetylene, and propane with oxygen as oxidizer. The choked flames were first generated following the quenching of an incident detonation after its interaction with cylindrical obstacles with two different blockage ratios, 75\% and 90\%. Comparison with a recently proposed model confirms that these are Chapman-Jouguet deflagrations. The subsequent acceleration was monitored via large-scale time-resolved shadowgraphy. The mechanism of transition was found to be through the amplification of transverse waves and hot spot ignition from local Mach reflections. The transition length was found to correlate very well with the mixture's sensitivity to temperature and pressure fluctuations. These fluctuations could be connected to a unique parameter (X), introduced by Radulescu. The parameter is the product of the non-dimensional activation energy (Ea/RT) and the ratio of chemical induction to reaction time (ti/tr). Mixtures with a higher X were found to be more prompt to hot spot ignition and amplification of the fast flame into detonations. The run-up distance for unstable mixtures was found to be much shorter than anticipated from a model neglecting the fluctuations in a 1-D framework. The run-up distance was also correlated to the detonation cell size, yielding LDDT ̃7 - 50 cells, with the proportionality coefficient depending on X and the obstacle blockage ratio. Finally, a unique correlation for the run-up distance is proposed, yielding LDDT ̃3000 c tr, where c is the sound speed in the shocked non-reacted gas, valid for large X.
Author: Mohamed Saifelislam Abdelgadir Ahmed
Publisher:
ISBN:
Category : University of Ottawa theses
Languages : en
Pages :
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Book Description
In the process of deflagration-to-detonation transition (DDT) in reactive gases, the flame typically accelerates first to the choked flame condition (known as a Chapman-Jouguet deflagration), where it propagates at the sound speed with respect to the product gases. Subsequently, the choked flame may transit to a detonation. In the present study, the transition length from choked flames to detonations was measured experimentally in laboratory-scale experiments in methane, ethane, ethylene, acetylene, and propane with oxygen as oxidizer. The choked flames were first generated following the quenching of an incident detonation after its interaction with cylindrical obstacles with two different blockage ratios, 75\% and 90\%. Comparison with a recently proposed model confirms that these are Chapman-Jouguet deflagrations. The subsequent acceleration was monitored via large-scale time-resolved shadowgraphy. The mechanism of transition was found to be through the amplification of transverse waves and hot spot ignition from local Mach reflections. The transition length was found to correlate very well with the mixture's sensitivity to temperature and pressure fluctuations. These fluctuations could be connected to a unique parameter (X), introduced by Radulescu. The parameter is the product of the non-dimensional activation energy (Ea/RT) and the ratio of chemical induction to reaction time (ti/tr). Mixtures with a higher X were found to be more prompt to hot spot ignition and amplification of the fast flame into detonations. The run-up distance for unstable mixtures was found to be much shorter than anticipated from a model neglecting the fluctuations in a 1-D framework. The run-up distance was also correlated to the detonation cell size, yielding LDDT ̃7 - 50 cells, with the proportionality coefficient depending on X and the obstacle blockage ratio. Finally, a unique correlation for the run-up distance is proposed, yielding LDDT ̃3000 c tr, where c is the sound speed in the shocked non-reacted gas, valid for large X.
Author:
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Category :
Languages : en
Pages :
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Book Description
The High-Temperature Combustion Facility at BNL was used to conduct deflagration-to-detonation transition (DDT) experiments. Periodic orifice plates were installed inside the entire length of the detonation tube in order to promote flame acceleration. The orifice plates are 27.3-cm-outer diameter, which is equivalent to the inner diameter of the tube, and 20.6-cm-inner diameter. The detonation tube length is 21.3-meters long, and the spacing of the orifice plates is one tube diameter. A standard automobile diesel engine glow plug was used to ignite the test mixture at one end of the tube. Hydrogen-air-steam mixtures were tested at a range of temperatures up to 650K and at an initial pressure of 0.1 MPa. In most cases, the limiting hydrogen mole fraction which resulted in DDT corresponded to the mixture whose detonation cell size, [lambda], was equal to the inner diameter of the orifice plate, d (e.g., d/[lambda]=1). The only exception was in the dry hydrogen-air mixtures at 650K where the DDT limit was observed to be 11 percent hydrogen, corresponding to a value of d/[lambda] equal to 5.5. For a 10.5 percent hydrogen mixture at 650K, the flame accelerated to a maximum velocity of about 120 mIs and then decelerated to below 2 mIs. By maintaining the first 6.1 meters of the vessel at the ignition end at 400K, and the rest of the vessel at 650K, the DDT limit was reduced to 9.5 percent hydrogen (d/[lambda]=4.2). This observation indicates that the d/[lambda]=1 DDT limit criteria provides a necessary condition but not a sufficient one for the onset of DDT in obstacle laden ducts. In this particular case, the mixture initial condition (i.e., temperature) resulted in the inability of the mixture to sustain flame acceleration to the point where DDT could occur. It was also observed that the distance required for the flame to accelerate to the point of detonation initiation, referred to as the run-up distance, was found to be a function of both the hydrogen mole fraction and the mixture initial temperature. Decreasing the hydrogen mole fraction or increasing the initial mixture temperature resulted in longer run-up distances. The density ratio across the flame and the speed of sound in the unburned mixture were found to be two parameters which influence the run-up distance.
Author: Stanley S. Grossel
Publisher: John Wiley & Sons
ISBN: 0470935642
Category : Technology & Engineering
Languages : en
Pages : 235
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Book Description
Designed for chemical engineers and other technical personnel involved in the design, operation, and maintenance of facilities and equipment where deflagration and detonation flame arresters (DDFAs) may be required, this book fosters effective application and operation of DDFAs through treatment of their principles of operation, selection, installation, and maintenance methods. This reference covers a broad range of issues concerning DDAs, including: An overview of deflagration and detonation prevention and protection practices An overview of combustion and flame propagation and how DDAs halt propagation Deflagration and detonation flame arrester technology Installation in process systems Regulations, codes, and standards Illustrative examples, calculations, and guidelines for DDA selection Appendices, including a glossary, a flame arrester specification sheet for vendor quotation, and a listing of flame arrester manufacturers.
Author: Joshua Allen Terry Gray
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
Publisher: Elsevier
ISBN: 0080962319
Category :
Languages : en
Pages : 3685
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Author: Paul Clavin
Publisher: Cambridge University Press
ISBN: 1107098688
Category : Mathematics
Languages : en
Pages : 723
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Book Description
A self-contained presentation of the dynamics of nonlinear waves in combustion and other non-equilibrium energetic systems for students and specialists.
Author: Gabriel Roy
Publisher: Butterworth-Heinemann
ISBN: 0123693942
Category : Business & Economics
Languages : en
Pages : 505
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Book Description
Chemical propulsion comprises the science and technology of using chemical reactions of any kind to create thrust and thereby propel a vehicle or object to a desired acceleration and speed. Cumbustion Processes in Propulsion focuses on recent advances in the design of very highly efficient, low-pollution-emitting propulsion systems, as well as advances in testing, diagnostics and analysis. It offers unique coverage of Pulse Detonation Engines, which add tremendous power to jet thrust by combining high pressure with ignition of the air/fuel mixture. Readers will learn about the advances in the reduction of jet noise and toxic fuel emissions-something that is being heavily regulated by relevant government agencies. Lead editor is one of the world's foremost combustion researchers, with contributions from some of the world's leading researchers in combustion engineering Covers all major areas of chemical propulsion-from combustion measurement, analysis and simulation, to advanced control of combustion processes, to noise and emission control Includes important information on advanced technologies for reducing jet engine noise and hazardous fuel combustion emissions
Author: Bernard Lewis
Publisher: Academic Press
ISBN: 1483258394
Category : Science
Languages : en
Pages : 754
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Book Description
Combustion, Flames, and Explosions of Gases, Second Edition focuses on the processes, methodologies, and reactions involved in combustion phenomena. The publication first offers information on theoretical foundations, reaction between hydrogen and oxygen, and reaction between carbon monoxide and oxygen. Discussions focus on the fundamentals of reaction kinetics, elementary and complex reactions in gases, thermal reaction, and combined hydrogen-carbon monoxide-oxygen reaction. The text then elaborates on the reaction between hydrocarbons and oxygen and combustion waves in laminar flow. The manuscript tackles combustion waves in turbulent flow and air entrainment and burning of jets of fuel gases. Topics include effect of turbulence spectrum and turbulent wrinkling on combustion wave propagation; ignition of high-velocity streams by hot solid bodies; burners with primary air entrainment; and description of jet flames. The book then takes a look at detonation waves in gases; emission spectra, ionization, and electric-field effects in flames; and methods of flame photography and pressure recording. The publication is a valuable reference for readers interested in combustion phenomena.
Author: CCPS (Center for Chemical Process Safety)
Publisher: John Wiley & Sons
ISBN: 1118265467
Category : Technology & Engineering
Languages : en
Pages : 436
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Book Description
This updated version of one of the most popular and widely used CCPS books provides plant design engineers, facility operators, and safety professionals with key information on selected topics of interest. The book focuses on process safety issues in the design of chemical, petrochemical, and hydrocarbon processing facilities. It discusses how to select designs that can prevent or mitigate the release of flammable or toxic materials, which could lead to a fire, explosion, or environmental damage. Key areas to be enhanced in the new edition include inherently safer design, specifically concepts for design of inherently safer unit operations and Safety Instrumented Systems and Layer of Protection Analysis. This book also provides an extensive bibliography to related publications and topic-specific information, as well as key information on failure modes and potential design solutions.
Author: Michael A. Liberman
Publisher: Springer Nature
ISBN: 3030851397
Category : Science
Languages : en
Pages : 620
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Book Description
This book provides the latest achievements and original research work in physics of combustion processes and application of the methods developed in combustion physics for astrophysical problems of stars burning, supernovae explosions and a confined thermonuclear fusion. All the materials in the book are presented in a concise and easily accessible way, but at the same time provides a deep physical inside in the phenomena considered. It is an effective theoretical course with the direct practical implications in engineering fields of engine’s development, energy production, safety issues inherent to terrestrial combustion, as well as in thermonuclear combustion in the inertial fusion. This book is aimed at university students, Ph.D. students and engineers, as well as professionals in combustion, energy-related research, astrophysics and researchers in neighboring fields.
