Download or read book Compressibility Effect on Turbulent Flames and Detonation Initiation and Propagation written by Jonathan Sosa and published by . This book was released on 2019 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work presents the first measurement of turbulent burning velocities of a highly-turbulent compressible standing flame induced by shock-driven turbulence in a Turbulent Shock Tube. High-speed schlieren, chemiluminescence, PIV, and dynamic pressure measurements are made to quantify flame-turbulence interaction for high levels of turbulence at elevated temperatures and pressure. Distributions of turbulent velocities, vorticity and turbulent strain are provided for regions ahead and behind the standing flame. The turbulent flame speed is directly measured for the high-Mach standing turbulent flame. From measurements of the flame turbulent speed and turbulent Mach number, transition into a non-linear compressibility regime at turbulent Mach numbers above 0.4 is confirmed, and a possible mechanism for flame generated turbulence and deflagration-to-detonation transition is established.

Download or read book Turbulence compressibility Dynamics of Fast Flames for Turbulence Induced Deflagration to detonation written by Jessica Chambers and published by . This book was released on 2021 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the fundamental mechanisms for detonation initiation is turbulence induced deflagration-to-detonation transition (tDDT). This research experimentally explores the dynamics of highly turbulent fast flames that are characterized by extremely high turbulent flame speeds, experience increased effects of compressibility, and may develop a runaway acceleration combined with a pressure buildup that leads to tDDT. The flame dynamics and reacting flow field are characterized using simultaneous high-speed particle image velocimetry, OH* chemiluminescence, pressure measurements, and schlieren imaging. We study various regimes of fast flame propagation conditions for runaway acceleration of turbulent fast flames and effects of compressibility on the evolution of these flames. When the local measured turbulent flame speed is found to be greater than the Chapman-Jouguet deflagration speed, the flame is categorized to be at the runaway transition regime that eventually leads to a detonation.

Download or read book Compressibility Mechanisms of Turbulent Flames and Detonations written by Hardeo Chin and published by . This book was released on 2021 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: Propulsion systems are influenced by the efficiency of combustion systems. One approach to substantially improve combustion efficiency is through pressure gain combustion or detonation-based engines. Detonations exhibit attractive features such as increased stagnation pressure and rapid heat release; however, their highly unsteady and three-dimensional nature makes them difficult to characterize. In addition, the deflagration state prior to detonation is not well defined experimentally. Detonations can be achieved via the deflagration-to-detonation transition (DDT), where a deflagration that propagates on the order of 1 - 10 m/s is accelerated to a detonation that propagates on the order of 2000 m/s. The DDT process is highly dynamic and can occur through several mechanisms such as the Zeldovich reactivity-gradient mechanism where hot spots are created by Mach stem reflections, localized vorticial explosions, boundary layer effects, or turbulence. This work focuses on transient compressible flame regimes within the turbulent DDT (tDDT) process which causes a flame to undergo various burning modes. These burning modes can be categorized into four regimes: (1) slow deflagrations, (2) fast deflagrations, (3) shock-flame complex, and (4) detonation. To achieve each burning mode, turbulence levels and propagation velocities are tailored using perforated plates and various fuel-oxidizer compositions. The primary goal of this dissertation is to characterize the relationship between the turbulent flame speed (ST) and Chapman-Jouguet (CJ) deflagration speed (SCJ) using high-speed optical diagnostics in a turbulent shock tube facility. This work will: (1) further validate and classify the turbulence-compressibility characteristics associated with fast flames that lead to detonation onset in a highly turbulent environment, (2) quantify local ST for fast flames, and (3) investigate the flow field conditions of flame modes relating to the SCJ criteria, from slow deflagrations to shock-flame complexes.

Download or read book Turbulent Combustion Modelling of Fast Flames and Detonations Using Compressible LEM LES written by Brian McNeilly Maxwell and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization of Fast Flames for Turbulence induced Deflagration to Detonation Transition written by Jessica Marcella Chambers and published by . This book was released on 2018 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the fundamental mechanisms for detonation initiation is turbulence driven deflagration to detonation transition (TDDT). The research experimentally explores the propagation dynamics demonstrated by fast deflagrated flames interacting with highly turbulent reactants. Fast flames produce extremely high turbulent flame speeds values, increased levels of compressibility and develop a runaway mechanism that leads to TDDT. The flame structural dynamics and reacting flow field are characterized using simultaneous high-speed particle image velocimetry, chemiluminescence, and Schlieren measurements. The investigation classifies the fast flame propagation modes at various regimes. The study further examines the conditions for a turbulent fast flame at the boundary of transitioning to quasi-detonation. The evolution of the flame-compressibility interactions for this turbulent fast flame is characterized. The local measured turbulent flame speed is found to be greater than the Chapman–Jouguet deflagration flame speed which categorizes the flame to be at the spontaneous transition regime and within the deflagration-to-detonation transition runaway process.

Download or read book Dynamics of Deflagrations and Reactive Systems written by A. L. Kuhl and published by AIAA. This book was released on 1991 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effects of Compressibility on the Propagation of Premixed Deflagration written by Andre Fecteau and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The thesis addresses the influence of compressible effects on the stability of deflagration waves. Due to the quasi-isobaric nature of slow flames, compressible effects in laminar flames are usually neglected. Nevertheless, turbulent deflagrations may propagate at substantially higher speeds, suggesting that compressible effects may play a role in their dynamics. In the present thesis, the stability of diffusion-dominated high-speed deflagrations is addressed. The deflagration is studied in the thickened regime, hence addressing the long wavelength limit of these deflagrations. The deflagrations are modelled by the compressible reactive Navier-Stokes equations with a single-step Arrhenius reaction model. The 2D stability of the steady traveling-wave solution is studied by direct simulation. It is found that, as the flame compressibility becomes significant, not only does the growth rates of the cellular profile of the deflagration waves increase, but the traditional correlation of the burning velocity and the flame surface area become far less strong. Significant compression regions form in front of the nonlinear flames. These compression regions have been found to increase the growth rates by increasing the temperature of the unburned gas in front of the flames, as well as convecting the flame forward. The results show that the flame propagation velocity in references to the unburned gas was significantly faster than the burning velocity. The vorticity was given consideration, as the compressibility of flame increase one can expect the baroclinic source to be of greater significance. The vorticity was show to, in effect, increase as compressibility increases while unexpectedly having a stabilizing direction of rotation on the cellular structure of the flames.

Download or read book Flame generated Turbulence for Flame Acceleration and Detonation Transition written by Rachel Hytovick and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Detonations are a supersonic mode of combustion witnessed in a variety of applications, from next-generation propulsion devices to catastrophic explosions and the formation of supernovas. Detonations are typically initiated through the deflagration to detonation transition (DDT), a detailed process where a subsonic flame undergoes rapid acceleration increasing compressibility until a hotspot forms on the flame front inciting a detonation wave to form. Due to the complex nature of the phenomena, DDT is commonly investigated in three stages -- (i) preconditioning, (ii) detonation onset, and (iii) wave propagation and stability. The research presented explores each of these stages individually, with a focus on preconditioning, to further resolve the governing mechanisms needed to initiate and sustain a detonation. More specifically, this work seeks to investigate the flow field and flame characteristics in reactions with increasing compressibility. Additionally, the research examines detonation onset and wave propagation to attain an all-encompassing concept of the DDT process. The work uses simultaneous high-speed diagnostics, consisting of particle image velocimetry (PIV), OH* chemiluminescence, schlieren and pressure measurements, to experimentally examine the preconditioning stage. For detonation onset and propagation, megahertz diagnostics (OH* chemiluminescence and schlieren) are implemented to quantitatively visualize the supersonic event. Through the comprehensive suite of diagnostics, this research deduces the role of turbulence in detonation onset to an ongoing cycle of flame generated compression that amplifies until the hotspot ignites.

Download or read book Combustion Phenomena written by Jozef Jarosinski and published by CRC Press. This book was released on 2009-02-12 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: Extensively using experimental and numerical illustrations, CombustionPhenomena: Selected Mechanisms of Flame Formation, Propagation, and Extinction provides a comprehensive survey of the fundamental processes of flame formation, propagation, and extinction. Taking you through the stages of combustion, leading experts visually display, mathematically explain, and clearly theorize on important physical topics of combustion. After a historical introduction to the field, they discuss combustion chemistry, flammability limits, and spark ignition. They also study counterflow twin-flame configuration, flame in a vortex core, the propagation characteristics of edge flames, instabilities, and tulip flames. In addition, the book describes flame extinction in narrow channels, global quenching of premixed flames by turbulence, counterflow premixed flame extinction limits, the interaction of flames with fluids in rotating vessels, and turbulent flames. The final chapter explores diffusion flames as well as combustion in spark- and compression-ignition engines. It also examines the transition from deflagration to detonation, along with the detonation wave structure. With downloadable resources of images that beautifully illustrate a range of combustion phenomena, this book facilitates a practical understanding of the processes occurring in the conception, spread, and extinguishment of a flame. It will help you on your way to finding solutions to real issues encountered in transportation, power generation, industrial processes, chemical engineering, and fire and explosion hazards.

Download or read book Irreversible Phenomena written by Kunio Terao and published by Springer Science & Business Media. This book was released on 2007-05-31 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ideals are simple and able to be easily understood, but never exist in reality. In this book a theory based on the second law of thermodynamics and its applications are described. In thermodynamics there is a concept of an ideal gas which satisfies a mathematical formula PV = RT. This formula can appro- mately be applied to the real gas, so far as the gas has not an especially high pressure and low temperature. In connection with the second law of thermo- namics there is also a concept of reversible and irreversible processes. The reversible process is a phenomenon proceeding at an infinitely low velocity, while the irreversible process is that proceeding with a finite velocity. Such a process with an infinitely slow velocity can really never take place, and all processes observed are always irreversible, therefore, the reversible process is an ideal process, while the irreversible process is a real process. According to the first law of thermodynamics the energy increase dU of the thermodynamic system is a sum of the heat dQ added to the system and work dW done in the system. Practically, however, the mathematical formula of the law is often expressed by the equation , or some similar equations derived from this formula, is applied to many phenomena. Such formulae are, however, th- retically only applicable to phenomena proceeding at an infinitely low velocity, that is, reversible processes or ideal processes.

Download or read book Gaseous Detonation Physics and Its Universal Framework Theory written by Zonglin Jiang and published by Springer Nature. This book was released on 2022-12-16 with total page 281 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights the theories and research progress in gaseous detonation research, and proposes a universal framework theory that overcomes the current research limitations. Gaseous detonation is an extremely fast type of combustion that propagates at supersonic speed in premixed combustible gas. Being self-sustaining and self-organizing with the unique nature of pressure gaining, gaseous detonation and its gas dynamics has been an interdisciplinary frontier for decades. The research of detonation enjoyed its early success from the development of the CJ theory and ZND modeling, but phenomenon is far from being understood quantitatively, and the development of theories to predict the three-dimensional cellular structure remains a formidable task, being essentially a problem in high-speed compressible reacting flow. This theory proposed by the authors’ research group breaks down the limitation of the one-dimensional steady flow hypothesis of the early theories, successfully correlating the propagation and initiation processes of gaseous detonation, and realizing the unified expression of the three-dimensional structure of cell detonation. The book and the proposed open framework is of high value for researchers in conventional applications such as coal mine explosions and chemical plant accidents, and state-of-the-art research fields such as supernova explosion, new aerospace propulsion engines, and detonation-driven hypersonic testing facilities. It is also a driving force for future research of detonation.

Download or read book Flame and detonation initiation and propagation in various hydrogen air mixtures with and without water spray written by L. W. Carlson and published by . This book was released on 1973 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Gasdynamics of Explosions and Reactive Systems written by A. K. Oppenheim and published by Elsevier. This book was released on 2013-10-22 with total page 787 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Handbook of Shock Waves Three Volume Set written by Gabi Ben-Dor and published by Elsevier. This book was released on 2000-10-18 with total page 2188 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Handbook of Shock Waves contains a comprehensive, structured coverage of research topics related to shock wave phenomena including shock waves in gases, liquids, solids, and space. Shock waves represent an extremely important physical phenomena which appears to be of special practical importance in three major fields: compressible flow (aerodynamics), materials science, and astrophysics. Shock waves comprise a phenomenon that occurs when pressure builds to force a reaction, i.e. sonic boom that occurs when a jet breaks the speed of sound.This Handbook contains experimental, theoretical, and numerical results which never before appeared under one cover; the first handbook of its kind.The Handbook of Shock Waves is intended for researchers and engineers active in shock wave related fields. Additionally, R&D establishments, applied science & research laboratories and scientific and engineering libraries both in universities and government institutions. As well as, undergraduate and graduate students in fluid mechanics, gas dynamics, and physics. Key Features* Ben-Dor is known as one of the founders of the field of shock waves* Covers a broad spectrum of shock wave research topics* Provides a comprehensive description of various shock wave related subjects* First handbook ever to include under one separate cover: experimental, theoretical, and numerical results

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1991 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book the influence of a compressible boundary on the propagation of gaseous detonations written by e. k. dabora and published by . This book was released on 1963 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Bending Effect in Turbulent Flame Propagation written by Girish Venkata Nivarti and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: