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Cellular Instability Of Diffusion Flames In The Counterflow Configuration
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Book Synopsis Cellular Instability of Diffusion Flames in the Counterflow Configuration by : Serguei Victorovich Kochevets
Download or read book Cellular Instability of Diffusion Flames in the Counterflow Configuration written by Serguei Victorovich Kochevets and published by . This book was released on 1999 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Instability on a Diffusion Flame Sustained by a Condensed-phase Fuel by : Tanya Tickel
Download or read book Instability on a Diffusion Flame Sustained by a Condensed-phase Fuel written by Tanya Tickel and published by . This book was released on 2006 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: An asymptotic method developed by Cheatham and Matalon in 2000 (Cheatham and Matalon 2000) is applied to a diffusion flame model whose fuel is present in its condensed phase. The thesis studies the effect that this form of supply has on the diffusion flame's stability, and finds three things: first, when the fuel feed rate corresponds to the rate of evaporation, the scale and onset of pulsating or traveling wave instabilities on the flame are the same. Second, vaporization can either mitigate or enhance the onset of cellular instability, depending on the fuel Lewis number and other factors, and suppresses smaller spatial wavenumbers for all parameter choices examined. Third, for extreme parameter values, the vaporization mechanism alone can cause an instability, even with complete combustion.
Book Synopsis On the Structure and Stability of Diffusion Flames by : Sally Ann Cheatham
Download or read book On the Structure and Stability of Diffusion Flames written by Sally Ann Cheatham and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Diffusion flames are flames in which fuel and oxidant, initially separate, come together to react chemically in a relatively thin combustion zone. Asymptotic methods, supplemented by numerical computation, are used to analyze the structure and dynamical properties of such flames. Attention is first focused on diffusion flames in arbitrary fluid flows for general fuel and oxidant Lewis numbers, in which the combustion is complete or nearly complete. Thus the limit of large Damkohler number and large activation energy is considered. The resulting mathematical formulation consists of a free boundary problem, with the flame as the free boundary. Such a treatment greatly simplifies the governing system of equations, and provides a framework for the analysis of the flame structure as well as its dynamical properties. The stability of a planar flame is next considered, with attention focused on diffusional-thermal effects. A dispersion relation is obtained, which relates the growth parameter and wavenumber of disturbances to the fuel and oxidant Lewis numbers, supply temperatures, and supply concentrations. Analysis of the dispersion relations indicates that instability corresponding to cellularity of the flame may occur for lean flames under near extinction conditions when the Lewis numbers of fuel and oxidant are sufficiently low. The asymptotic model is also used to identify conditions under which flame extinction occurs. In particular, the burning characteristics of a dilute spray diffusion flame have been examined. The presence of fuel droplets in the fuel supply is shown to alter the extinction characteristics of the flame. The onset of oscillations in the spherical diffusion flame surrounding a fuel droplet is also considered. Motivated by recent microgravity candle flame experiments, the constraint of a weak oxidant environment is imposed. A linear stability analysis indicates that oscillations may indeed result when radiative heat losses and the Lewis numbers of fuel and oxidant are sufficiently large. Estimates for the critical conditions are given, along with a prediction of the resulting frequency of oscillation. A weakly non-linear analysis is then used to more fully investigate the transition to an oscillatory burning state.
Book Synopsis The Structure and Extinction of Counterflow Flames by : Ishwar Kanwar Puri
Download or read book The Structure and Extinction of Counterflow Flames written by Ishwar Kanwar Puri and published by . This book was released on 1987 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Cellular Instability Phenomenon in Premixed Tubular Flames and Non-premixed Opposed Tubular Flames by : Yu Wang
Download or read book Cellular Instability Phenomenon in Premixed Tubular Flames and Non-premixed Opposed Tubular Flames written by Yu Wang and published by . This book was released on 2008 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NBSIR. written by and published by . This book was released on 1978 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Third Annual Conference on Fire Research by :
Download or read book Third Annual Conference on Fire Research written by and published by . This book was released on 1979 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Dynamics and Statistics of Cellular Instability in Laminar and Turbulent Expanding Flames by : Zirui Liu
Download or read book Dynamics and Statistics of Cellular Instability in Laminar and Turbulent Expanding Flames written by Zirui Liu and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation consists of a series of studies on the dynamics and statistics of the cellular instability in both laminar and turbulent expanding flames. First of all, local quantities including the flame-induced velocity, curvature and strain rates of the cellularly-unstable laminar expanding flames have been measured for the first time to our knowledge. The statistics of these quantities and their relations with the global flame propagation have been investigated. Then, the flow field induced by the cellularly-unstable laminar expanding flames has been further processed to address the hypothesis of self-turbulization. The flow field near the unstable flamefront exhibits turbulence-like characteristics, and a power-law scaling relation in the energy spectra of tangential velocities on the flamefront have been discovered. It is demonstrated theoretically that such scaling relation is caused by the fractal nature of the wrinkled flame surface. Next, in light of the knowledge of cellular instability in laminar expanding flames, the effects of cellular instability in turbulent expanding flames have been studied thereafter. A scaling analysis has been conducted to show the interaction between Darrieus-Landau instability and turbulence in different regimes of the turbulent flame regime diagram. The turbulent flame speeds have also been measured in these regimes to validate the scaling analysis. Furthermore, the effect of the diffusional-thermal instability has also been investigated experimentally. It is shown that Darrieus-Landau instability controls the flame acceleration, while diffusional-thermal instability affects the magnitude of the flame speed. Next, the local statistics of the turbulent cellularly-unstable expanding flames in the corrugated flamelet regime have been studied, and the interaction between cellular instability and turbulence are assessed based on the statistics of the strain rates, the curvature and the surface spectra.
Book Synopsis Experimental Studies of Inhibited Counterflow Flames by : Leonard F. Truett
Download or read book Experimental Studies of Inhibited Counterflow Flames written by Leonard F. Truett and published by . This book was released on 2001 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Combustion Instabilities in Non-premixed Opposed-flow Tubular Flames by : Scott William Shopoff
Download or read book Combustion Instabilities in Non-premixed Opposed-flow Tubular Flames written by Scott William Shopoff and published by . This book was released on 2010 with total page 85 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Structure of Counter-flow Diffusion Flames by : T. David
Download or read book The Structure of Counter-flow Diffusion Flames written by T. David and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Effects of Inert Gases and Flow Velocities on the Structure and Stability of Coflow Diffusion Flames by : Daniel Tomio Souza
Download or read book Effects of Inert Gases and Flow Velocities on the Structure and Stability of Coflow Diffusion Flames written by Daniel Tomio Souza and published by . This book was released on 2021 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: A deeper understanding of flame stabilization and extinguishing mechanisms is necessary in developing the next generation of flame suppressants. In order to understand the effects of inert gases on coflow diffusion flames, a 28-mm diameter cup burner was used to generate methane and propane coflow diffusion flames. The measured minimum extinguishing concentration of N2 added to the coflow air was 28.5 +/- 0.05 % and 34.0 +/- 0.07 % for methane and propane, respectively, and those for CO2 were 17.2 +/- 0.12 % and 22.4 +/- 0.06 %, respectively. Silica-coated, 50-um R-type thermocouples were used to measure temperature in the flames as N2 or CO2 was added to the coflow air. Thin filament pyrometry technique using a 15-um SiC fiber was also applied in an attempt to measure the temperature of the inert gas-added flames. For calibrations of the temperature measurements, a 25.4-mm x 25.4-mm Hencken burner was used to produce a near-adiabatic initially unmixed methane flame. In addition to the thermal flame structure measurements, the stability limits of laminar jet diffusion flames were measured for various fuels (methane, ethane, ethylene, acetylene propane, butane, and 1-butene) to further elaborate the effects of flow velocities on diffusion flame stabilization and extinguishing mechanisms. Through these experimental techniques, the temperature effects of inert gases on coflow diffusion flames were observed and factors leading to instability in laminar jet diffusion flames were identified.
Book Synopsis Physical and Chemical Processes in Flames by : Chung K. Law
Download or read book Physical and Chemical Processes in Flames written by Chung K. Law and published by . This book was released on 2001 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objectives of the present program are to develop detailed and simplified chemical kinetics model for hydrocarbon combustion, and to understand and quantify the dynamics of flames. During the reporting period progress were made in the following projects: (1) Laminar flame speeds of mixtures of ethylene and n-butane were studied. Results suggest the dominant influence of the adiabatic flame temperature in assessing the mixture flame speed. (2) A theory of complex CSP (computational singular perturbation) for chemistry reduction and analysis was developed. An algorithm was derived through which detailed mechanisms can be systematically reduced to simpler ones without compromising the comprehensiveness of the original mechanism. (3) Stretch effects on premixed flame pulsation were computationally and analytically studied. Results show that positive (negative) stretch promotes (retards) the development of pulsating instability, which is completely opposite to the influence of stretch on cellular instability. (4) Pulsating instability of near-limit diffusion flames were computationally studied. Results show that the instability and the subsequent extinction of methane and hydrogen flames assume the characteristics of diffusion and premixed flames respectively.
Book Synopsis A Gallery of Combustion and Fire by : Charles E. Baukal, Jr.
Download or read book A Gallery of Combustion and Fire written by Charles E. Baukal, Jr. and published by Cambridge University Press. This book was released on 2020-09-03 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: A Gallery of Combustion and Fire is the first book to provide a graphical perspective of the extremely visual phenomenon of combustion in full color. It is designed primarily to be used in parallel with, and supplement existing combustion textbooks that are usually in black and white, making it a challenge to visualize such a graphic phenomenon. Each image includes a description of how it was generated, which is detailed enough for the expert but simple enough for the novice. Processes range from small scale academic flames up to full scale industrial flames under a wide range of conditions such as low and normal gravity, atmospheric to high pressures, actual and simulated flames, and controlled and uncontrolled flames. Containing over 500 color images, with over 230 contributors from over 75 organizations, this volume is a valuable asset for experts and novices alike.
Book Synopsis Major Research Topics in Combustion by : M.Y. Hussaini
Download or read book Major Research Topics in Combustion written by M.Y. Hussaini and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 668 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Institute for Computer Applications in Science and Engineer ing (ICASE) and NASA Langley Research Center (LaRC) brought together on October 2-4, 1989 experts in the various areas of com bustion with a view to expose them to some combustion problems of technological interest to LaRC and possibly foster interaction with the academic community in these research areas. The top ics chosen for this purpose were flame structure, flame stability, flame holding/extinction, chemical kinetics, turbulence-kinetics in teraction, transition to detonation, and reacting free shear layers. The lead paper set the stage by discussing the status and issues of supersonic combustion relevant to scramjet engine. Then the ex perts were called upon i) to review the current status of knowledge in the aforementioned ;:I. reas, ii) to focus on how this knowledge can be extended and applied to high-speed combustion, and iii) to suggest future directions of research in these areas. Each topic was then dealt with in a position paper followed by formal discussion papers and a general discussion involving the participants. The position papers discussed the state-of-the-art with an emphasis on key issues that needed to be resolved in the near future. The discussion papers crit ically examined these issues and filled in any lacunae therein. The edited versions of the general discussions in the form of questions from the audience and answers from the speakers are included wher ever possible to give the reader the flavor of the lively interactions that took place.
Book Synopsis On the Cellular Instability of Flames Near Porous-plug Burners by : A.C. McIntosh
Download or read book On the Cellular Instability of Flames Near Porous-plug Burners written by A.C. McIntosh and published by . This book was released on 1984 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Study of Transient Counterflow Diffusion Flames with Radiation by : Tariq Shamim
Download or read book A Study of Transient Counterflow Diffusion Flames with Radiation written by Tariq Shamim and published by . This book was released on 1997 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt:
