Download or read book Fluid Dynamic Structures in Diffusion Flames written by A. Cabelli and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Experiments were carried out in a combustion facility which allowed optical and other measurements to be made on a diffusion flame formed by a jet of fuel gas and a co-flowing jet of air. Acoustic perturbations could be imposed to the flow of fuel with a loudspeaker mounted at the bottom of a settling chamber in the fuel line. A two mirror schlieren system was used to image the gas flames and a colour filter was placed at the focus of the second mirror to produce coloured schlieren images when a continuous white light source was used. Two types of coherent structures were observed, located concentrically along the axis of the flame. The outer structures, found outside the luminous part of the flame, outlined the boundary between products of combustion and the cold airstream, while the inner structures, located well inside the luminous flame, marked the interface between the cold fuel and the reaction zone. The structures were periodic and their frequencies identified by spectral analysis of optical and pressure signals. The signal from a pressure probe placed in the flame and from a phototransistor focused at the corresponding position in the schlieren image, correlated well. Over the range of Reynolds numbers tested, the outer structures exhibited a dominant frequency of approximately 13 Hz whereas the faster inner structures occurred at approximately 256 Hz. Acoustic excitation at these frequencies made the corresponding structures more coherent and influenced the development of the instability close to the nozzle exit. The response of the experimental equipment to band limited white noise, with the jet not ignited, revealed spectral peaks at the frequency of the inner structures which confirm the nexus between the flow and the acoustic field (even without external excitation). The wavelength of these structures (and their convection velocity) did not vary over the range of Reynolds numbers considered, at a given distance from the nozzle exit, but increased slightly with axial position. When the flame was acoustically forced at a frequency different from the preferred frequency, their wavelength remained unchanged but the velocity changed to accommodate the change in frequency.
Download or read book Fluid Mechanics Aspects of Fire and Smoke Dynamics in Enclosures written by Bart Merci and published by CRC Press. This book was released on 2022-10-24 with total page 355 pages. Available in PDF, EPUB and Kindle. Book excerpt: - written by world leading experts in the field - contains many worked-out examples, taken from daily life fire related practical problems - covers the entire range from basics up to state-of-the-art computer simulations of fire and smoke related fluid mechanics aspects, including the effect of water - provides extensive treatment of the interaction of water sprays with a fire-driven flow - contains a chapter on CFD (Computational Fluid Dynamics), the increasingly popular calculation method in the field of fire safety science
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 Turbulent Combustion Modeling written by Tarek Echekki and published by Springer Science & Business Media. This book was released on 2010-12-25 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent combustion sits at the interface of two important nonlinear, multiscale phenomena: chemistry and turbulence. Its study is extremely timely in view of the need to develop new combustion technologies in order to address challenges associated with climate change, energy source uncertainty, and air pollution. Despite the fact that modeling of turbulent combustion is a subject that has been researched for a number of years, its complexity implies that key issues are still eluding, and a theoretical description that is accurate enough to make turbulent combustion models rigorous and quantitative for industrial use is still lacking. In this book, prominent experts review most of the available approaches in modeling turbulent combustion, with particular focus on the exploding increase in computational resources that has allowed the simulation of increasingly detailed phenomena. The relevant algorithms are presented, the theoretical methods are explained, and various application examples are given. The book is intended for a relatively broad audience, including seasoned researchers and graduate students in engineering, applied mathematics and computational science, engine designers and computational fluid dynamics (CFD) practitioners, scientists at funding agencies, and anyone wishing to understand the state-of-the-art and the future directions of this scientifically challenging and practically important field.
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.
Download or read book Experimental and Computational Study of Fluid Dynamics combustion Coupling in a Diffusion Flame vortex Ring Interaction written by Shin-Juh Chen and published by . This book was released on 2000 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computational Fluid Dynamics in Fire Engineering written by Guan Heng Yeoh and published by Butterworth-Heinemann. This book was released on 2009-04-20 with total page 545 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fire and combustion presents a significant engineering challenge to mechanical, civil and dedicated fire engineers, as well as specialists in the process and chemical, safety, buildings and structural fields. We are reminded of the tragic outcomes of ‘untenable’ fire disasters such as at King’s Cross underground station or Switzerland’s St Gotthard tunnel. In these and many other cases, computational fluid dynamics (CFD) is at the forefront of active research into unravelling the probable causes of fires and helping to design structures and systems to ensure that they are less likely in the future. Computational fluid dynamics (CFD) is routinely used as an analysis tool in fire and combustion engineering as it possesses the ability to handle the complex geometries and characteristics of combustion and fire. This book shows engineering students and professionals how to understand and use this powerful tool in the study of combustion processes, and in the engineering of safer or more fire resistant (or conversely, more fire-efficient) structures. No other book is dedicated to computer-based fire dynamics tools and systems. It is supported by a rigorous pedagogy, including worked examples to illustrate the capabilities of different models, an introduction to the essential aspects of fire physics, examination and self-test exercises, fully worked solutions and a suite of accompanying software for use in industry standard modeling systems. Computational Fluid Dynamics (CFD) is widely used in engineering analysis; this is the only book dedicated to CFD modeling analysis in fire and combustion engineering Strong pedagogic features mean this book can be used as a text for graduate level mechanical, civil, structural and fire engineering courses, while its coverage of the latest techniques and industry standard software make it an important reference for researchers and professional engineers in the mechanical and structural sectors, and by fire engineers, safety consultants and regulators Strong author team (CUHK is a recognized centre of excellence in fire eng) deliver an expert package for students and professionals, showing both theory and applications. Accompanied by CFD modeling code and ready to use simulations to run in industry-standard ANSYS-CFX and Fluent software
Download or read book Turbulent Mixing in Nonreactive and Reactive Flows written by S. Murthy and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 469 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence, mixing and the mutual interaction of turbulence and chemistry continue to remain perplexing and impregnable in the fron tiers of fluid mechanics. The past ten years have brought enormous advances in computers and computational techniques on the one hand and in measurements and data processing on the other. The impact of such capabilities has led to a revolution both in the understanding of the structure of turbulence as well as in the predictive methods for application in technology. The early ideas on turbulence being an array of complicated phenomena and having some form of reasonably strong coherent struc ture have become well substantiated in recent experimental work. We are still at the very beginning of understanding all of the aspects of such coherence and of the possibilities of incorporating such structure into the analytical models for even those cases where the thin shear layer approximation may be valid. Nevertheless a distinguished body of "eddy chasers" has come into existence. The structure of mixing layers which has been studied for some years in terms of correlations and spectral analysis is also getting better understood. Both probability concepts such as intermittency and conditional sampling as well as the concept of large scale structure and the associated strain seem to indicate possibilities of distinguishing and synthesizing 'engulfment' and molecular mixing.
Download or read book Combustion Theory written by Forman A. Williams and published by CRC Press. This book was released on 2018-03-05 with total page 705 pages. Available in PDF, EPUB and Kindle. Book excerpt: Combustion Theory delves deeper into the science of combustion than most other texts and gives insight into combustions from a molecular and a continuum point of view. The book presents derivations of the basic equations of combustion theory and contains appendices on the background of subjects of thermodynamics, chemical kinetics, fluid dynamics, and transport processes. Diffusion flames, reactions in flows with negligible transport and the theory of pre-mixed flames are treated, as are detonation phenomena, the combustion of solid propellents, and ignition, extinction, and flamibility pehnomena.
Download or read book Theories of Turbulent Combustion in High Speed Flows written by Paul A. Libby and published by . This book was released on 1995 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulent Premixed Flames written by Nedunchezhian Swaminathan and published by Cambridge University Press. This book was released on 2011-04-25 with total page 447 pages. Available in PDF, EPUB and Kindle. Book excerpt: A work on turbulent premixed combustion is important because of increased concern about the environmental impact of combustion and the search for new combustion concepts and technologies. An improved understanding of lean fuel turbulent premixed flames must play a central role in the fundamental science of these new concepts. Lean premixed flames have the potential to offer ultra-low emission levels, but they are notoriously susceptible to combustion oscillations. Thus, sophisticated control measures are inevitably required. The editors' intent is to set out the modeling aspects in the field of turbulent premixed combustion. Good progress has been made on this topic, and this cohesive volume contains contributions from international experts on various subtopics of the lean premixed flame problem.
Download or read book Combustion Technologies for a Clean Environment written by Maria G. da Graca Carvalho and published by CRC Press. This book was released on 2022-03-23 with total page 864 pages. Available in PDF, EPUB and Kindle. Book excerpt: Selected Papers from the Proceedings of the First International Conference Vilamoura, Portugal, September 3-6, 1991. The 54 papers in this volume establish the first in a series of biannual benchmarks for technologies that maximize energy conversion while minimizing undesirable emissions. Covering the entire range of industrial and transport combustion as well as strategies for energy R&D, these contributions will be useful to mechanical and chemical engineers in academia and industry, and technical personnel in military, energy and environmental agencies of government. Among topics covered in the book are: strategies: now and in the future; pulverised coal combustion; oil combustion; gas combustion; gas fired systems, biomass combustion; fluidized bed combustion; incinerators; internal combustion; engines and reaction kinetics.
Download or read book Fluid Dynamical Aspects of Combustion Theory written by M. Onofri and published by . This book was released on 1991 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Research Note contains papers presented in a series of seminars held at the Istituto per le Applicazioni del Calcolo M. Picone of the Italian National Research Council (CNR), during the special year devoted to Fluid Dynamical Aspects of Combustion Theory.
Download or read book Energy and Combustion Science written by N. A. Chigier and published by Elsevier. This book was released on 2013-10-22 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt: Energy and Combustion Science is a collection of papers that covers advancement in the field of energy and combustion science. The materials presented in the book are organized thematically into parts. The text first covers the issues, concerns, problems of the contemporary combustion technology. The subsequent parts of the book cover various areas in combustions science, namely, pollution, gas, oil, coal, and engines. Most of the articles in the book are concerned with the byproduct of fuel combustion. The text will be of great use to students, researchers, and practitioners of disciplines that deal with the energy and combustion technology.
Download or read book Structure of Confined Laminar Spray Diffusion Flames numerical Investigation written by M. A. Mawid and published by . This book was released on 1993 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1965 with total page 654 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Lagrangian Fluid Dynamics for Combustion Modelling written by Martin J. Fritts and published by . This book was released on 1981 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent flow visualization experiments have shown the need to follow the behavior of dynamically interacting coherent structures in both cold flows and flames. Since these structures move the fluid, a Lagrangian approach is especially useful in theoretical calculations because we can observe the interaction of a particular fluid element with its changing environments as the flow evolves. One-dimensional Lagrangian flame models are successful because they also minimize the effects of numerical diffusion which is the bane of laminar flame calculations. However, most two- and three-dimensional flame models are Eulerian because of problems in standard Lagrangian formulations for multi-dimensional models and because phenomenological turbulent diffusion terms are usually added which mask the numerical diffusion. The purpose of this paper is to describe one- and multi-dimensional Lagrangian algorithms which eliminate many of the problems previously associated with this approach. An example of a one-dimensional flame calculation which incorporates the new ideas will be given. Finally, examples will be given of the two-dimensional Lagrangian triangular gridding technique and it will be indicated how this may be applied to multi-phase combustion problem. (Author).
