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Experimental Study Of The Flowfield Of A V Shaped Premixed Turbulent Flame
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Book Synopsis Experimental Study of the Flowfield of a V-shaped Premixed Turbulent Flame by :
Download or read book Experimental Study of the Flowfield of a V-shaped Premixed Turbulent Flame written by and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The flowfield of a V-shaped, premixed ethylene/air flame in grid induced turbulence has been studied using Laser Doubler Velocimetry. The experimental conditions covered free-stream velocities of 5 and 7 m/s and equivalence ratios ranging from 0.6 to 0.78. The two-dimensional velocity vectors obtained indicate that flow deflection in the free stream was significant and seemed to correlate with the flame angle. The influence of the flame holder wake on the flame was demonstrated. In the presence of the flame, an increase in the turbulence level in the free stream was found and was attributed to fluctuations in flow deflection induced by the fluctuating flame.
Book Synopsis AN EXPERIMENTAL STUDY OF THE FLOW FIELD OF A TWO DIMENSIONAL PREMIXED TURBULENT FLAME. by :
Download or read book AN EXPERIMENTAL STUDY OF THE FLOW FIELD OF A TWO DIMENSIONAL PREMIXED TURBULENT FLAME. written by and published by . This book was released on 1980 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: A turbulent reacting shear layer in a premixed propane/air flow has been studied in a two dimensional combustor, with the flame stabilized behind a rearward facing streamlined step. Spark shadowgraphs show that in the range of velocities (7.5 to 22.5 m/sec corresponding to Reynolds numbers of .5 x 104 cm−1 to 1. 5 x 104 cm−1) and equivalence ratios (0.4 to 0.7) studied, the mixing layer is dominated by Brown~ Roshko type large coherent structures in both reacting and nonreacting flows. High speed schlieren movies show that these eddies are convected downstream and increase their size and spacing by combustion and coalescence with neighboring eddies. Tracing individual eddies shows, in the reacting shear layer, that, on the average, eddies accelerate as they move downstream with the highest acceleration close to the origin of the shear layer. Combustion is confined to these large structures which develop as a result of vortical action of the shear flow. On the average, the reacting eddies have a lower growth rate than nonreacting eddies. A turbulent boundary layer created by means of a tripping wire upstream of the edge of the step virtually eliminates the large coherent structures in the shear layer, while for the case in which the wire could not trigger the transition to turbulence, the large coherent structures dominated the reacting and nonreacting flows.
Book Synopsis Experimental Study of Turbulent Premixed Combustion in V-shaped Flames by : Sina Kheirkhah
Download or read book Experimental Study of Turbulent Premixed Combustion in V-shaped Flames written by Sina Kheirkhah and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Characteristics of turbulent premixed flames were investigated experimentally. The investigations were performed using Mie scattering, Particle Image Velocimetry, Rayleigh scattering, and broad-band luminosity imaging techniques. Methane-air flames associated with a relatively wide range of turbulence intensities, fuel-air equivalence ratios, and mean bulk flow velocities were investigated. For a relatively moderate value of turbulence intensity, a new concept is introduced and utilized to provide a detailed description associated with interaction of turbulent flow and flame front. The concept pertains to reactants velocity estimated at the vicinity of the flame front and is referred to as the edge velocity. Specifically, it is shown that fluctuations of the flame front position are induced by fluctuations of the edge velocity. For a relatively wide range of turbulence intensity, several characteristics of turbulent premixed flames, namely, front topology, brush thickness, surface density, and consumption speeds are investigated. For the first time, several flame front structures are identified and studied. It is shown that, due to formation of these front structures, the regime of turbulent premixed combustion transitions from the regime of counter-gradient diffusion to that of the gradient diffusion. In addition to these, a comprehensive study is performed to investigate influence of flame configuration on several flame front characteristics. It is obtained that, although changing the flame configuration influences several flame characteristics, the trends associated with the effects of governing parameters on the characteristics are nearly independent of the flame configuration.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1981 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1981 with total page 1370 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Book Synopsis Combustion Phenomena by : Jozef Jarosinski
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 Fossil Energy Update written by and published by . This book was released on 1981 with total page 698 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Experimental Study of Burner Stabilized Turbulent Flames in Premixed Reactants by : M. D. Fox
Download or read book An Experimental Study of Burner Stabilized Turbulent Flames in Premixed Reactants written by M. D. Fox and published by . This book was released on 1962 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: Current concepts of flame propagation in premixed, turbulent gas streams are examined. This leads to the conclusion that the link between theory and experiment is entirely inadequate and incapable of improvement by existing methods. A series of new methods is implemented in an attempt to short-circuit the unprofitable chain of hypothesis and experiment which has hampered the identification of dubious steps. Methods of introducing uniform turbulence at relatively slow flows and improvements in light sources allow analysis of the approach flow by photographing particles illuminated by an interrupted Tyndall beam. Three new optical deflection methods are used to give a measure of the randomness of flame-front orientation, of the time-mean structure of the flame and of the instantaneous shape of the corrugated front. It is found that this corrugated surface propagates at a velocity considerably in excess of the normal laminar burning velocity. Quantitative analysis of the frequency of "peaks" and "valleys" on the surface, together with comparative data from the apex of laminar flames, suggests an explanation in terms of the effects of curvature and, secondarily, of the influence of small scale turbulence.
Book Synopsis An Experimental Study of Isolated Turbulent Flame Puffs with a Co-flow by : J. C. Hermanson
Download or read book An Experimental Study of Isolated Turbulent Flame Puffs with a Co-flow written by J. C. Hermanson and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Experimental Study of Flamelet Surfaces in Turbulent Combustion by :
Download or read book An Experimental Study of Flamelet Surfaces in Turbulent Combustion written by and published by . This book was released on 1990 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: The major objective of the research reported was to study the properties of constant scalar property surfaces in turbulent reacting flows. Two dimensional image measurements were made in premixed turbulent flames and in jets and jet flames. Point-in-space, time-series measurements were also made, and the data used to study the properties of surface crossing statistics in jets and premixed flames. In addition, the hypothesis that, for the purpose of estimating the mean surface area per unit volume, surfaces in turbulent flow can be represented by fractal surfaces was used to develop models for the mean chemical reaction rate in premixed flames and for the source term in the equation for intermittency in free jets. Also a new method for making conditional velocity measurements in premixed flames was developed and applied to obtain unique data for velocity in these flames and to study jumps, across flamelets, of certain velocity statistics. Major findings for the flows and conditions studied include: (1) for the premixed case flamelet surfaces are fractal as are constant mixture fraction surfaces in jets and constant temperature surfaces in jet flames; (2) in jets the surface fractal dimension is between 2.3 to 2.4; (3) level crossing sets from time-series data are not simple fractal sets; (4) the idea of fractal bursts is introduced to help interpret the crossing sets; and (5) unique fully-conditional velocity data give a measure of velocity jumps across flamelets in premixed combustion.
Book Synopsis Experimental Study of Flow and Turbulence in a V-flame Burner and a S.I. Engine by : Kazem Atashkari
Download or read book Experimental Study of Flow and Turbulence in a V-flame Burner and a S.I. Engine written by Kazem Atashkari and published by . This book was released on 1997 with total page 498 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental Investigation of Flow Turbulence Effects on Premixed Methane-air Flames by : Kenneth Owen Smith
Download or read book Experimental Investigation of Flow Turbulence Effects on Premixed Methane-air Flames written by Kenneth Owen Smith and published by . This book was released on 1978 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experiments in Laminar and Turbulent Premixed Counter-flow Flames at Variable Lewis Number by : Sean Salusbury
Download or read book Experiments in Laminar and Turbulent Premixed Counter-flow Flames at Variable Lewis Number written by Sean Salusbury and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "This thesis examines preferential diffusion effects in laminar and turbulent premixed combustion. Stretched, fuel-lean, laminar flames of methane, propane and hydrogen are studied experimentally in a counter-flow flame configuration to investigate the effect of Lewis number on stretched flames. Laminar flame results show that a maximum reference flame speed exists for mixtures with Le >= 1 at lower flame-stretch values than the extinction stretch rate. A continually-increasing reference flame speed is measured for Le “ 1 mixtures until extinction occurs when the flame is constrained by the stagnation point.Turbulent counter-flow flame experiments are then performed for these mixtures, using high-blockage turbulence-generating plates to produce turbulence intensities on the order of u'/sLo = 1 to 10. Measurements of average and instantaneous velocity within the turbulent flame are performed by time-resolved particle image velocimetry measurements. Average and instantaneous flame front position is also measured by Rayleigh spectroscopy.Measurements of average turbulent burning velocity demonstrate the ambiguity in definitions of the burning velocity and the difficulty of examining turbulent flame chemistry using averaged measurements. Instantaneous statistics are shown to be superior tools for studying turbulent combustion. The probability-density functions (PDF) of the local flamelet burning velocities for Le >= 1 mixtures show that the instantaneous flamelet burning velocities increase with increasing turbulence intensity and flame stretch. The PDF for the Le ~= 1 mixture has a sharply skewed shape at high turbulence intensity and has a sharp drop-off in probability at a velocity that corresponds with the experimentally-measured maximum reference flame speed from the laminar flame experiments. In contrast, in the Le “ 1 turbulent flames, the most-probable instantaneous flamelet burning velocities increase with increasing turbulence intensity and can significantly exceed the maximum reference flame speed measured in counter-flow laminar flames at extinction.These results are reinforced by instantaneous flame position measurements. Flame front location PDFs show the most probable flame location to be linked to velocity PDFs. Furthermore, hydrogen PDFs are recognizably skewed as u'/sLo increases, indicating a tendency for the Le “ 1 mixture to propagate farther into the unburned reactants. These results support the leading edge theory of premixed turbulent flame propagation for flames in which preferential diffusion effects are expected.In the study of turbulent flames, this work promotes the use of local, instantaneous statistics as a tool for describing experimental results and studying fuel chemistry." --
Download or read book Flame Structure written by M. D. Fox and published by . This book was released on 1961 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt: Current concepts of flame propagation in premixed, turbulent gas streams are examined. This leads to the conclusion that the link between theory and experiment is entirely inadequate and incapable of improvement by existing methods. A series of new method is implemented in an attempt to short-circuit the unprofitable chain of hypothesis and experiment which has hampered the identification of dubious steps. Methods of introducing uniform turbulence at relatively slow flows and improvements in light sources allow analysis of the approach flow by photographing particles illuminated by an interrupted Tyndall beam. Three new optical deflection methods are used to give a measure of the randomness of flame-front orientation, of the time-mean structure of the flame and of the instantaneous shape of the corrugated front. It is found that this corrugated surface propagates at a velocity considerably in excess of the normal laminar burning velocity. Quantitative analysis of the frequency of 'peaks' and 'valleys' on the surface, together with comparative data from the apex of laminar flames, suggests an explanation in terms of the effects of curvature and, secondarily, of the influence of small scale turbulence. (Author).
Download or read book American Laboratory written by and published by . This book was released on 1982 with total page 1108 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Premixed Turbulent Flame Propagation by : D. A. Santavicca
Download or read book Premixed Turbulent Flame Propagation written by D. A. Santavicca and published by . This book was released on 1990 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of an experimental study of turbulence-flame interactions and their effect on turbulent flame propagation are reported. Experiments are conducted in a new turbulent flow system which is capable of producing relative turbulence intensities as high as 100 percent. Using a freely propagating, one-dimensional flame configuration, measurements are made using LDV of the mean velocity, turbulence intensity, integral time scale, energy spectrum, Reynolds stress, and integral length scale, at a fixed location both before and after flame arrival. A complete set os such measurements has been made at one operating condition which characterize both the magnitude of flame generated turbulence and its anisotropic nature. The freely propagating, one dimensional flame configuration has also been used to study the effect of turbulence on turbulent flame structure. Two dimensional Mie scattering is used to obtain a two-dimensional slice of the turbulent flame surface. Such measurements have been made at 15 different conditions over very broad range of turbulence Reynolds and Damkohler numbers and have been analyzed to determine the fractal nature of the turbulent flame surface. The results of these measurements show that premixed turbulent flame surfaces are fractal throughout the reaction sheet regime. Keywords: Premixed turbulent combustion; Turbulent flame interactions; Turbulent flame propagation; Turbulent flame structure. (JHD).
Book Synopsis Turbulent Reactive Flows by : R. Borghi
Download or read book Turbulent Reactive Flows written by R. Borghi and published by Springer Science & Business Media. This book was released on 2013-03-08 with total page 958 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent reactive flows are of common occurrance in combustion engineering, chemical reactor technology and various types of engines producing power and thrust utilizing chemical and nuclear fuels. Pollutant formation and dispersion in the atmospheric environment and in rivers, lakes and ocean also involve interactions between turbulence, chemical reactivity and heat and mass transfer processes. Considerable advances have occurred over the past twenty years in the understanding, analysis, measurement, prediction and control of turbulent reactive flows. Two main contributors to such advances are improvements in instrumentation and spectacular growth in computation: hardware, sciences and skills and data processing software, each leading to developments in others. Turbulence presents several features that are situation-specific. Both for that reason and a number of others, it is yet difficult to visualize a so-called solution of the turbulence problem or even a generalized approach to the problem. It appears that recognition of patterns and structures in turbulent flow and their study based on considerations of stability, interactions, chaos and fractal character may be opening up an avenue of research that may be leading to a generalized approach to classification and analysis and, possibly, prediction of specific processes in the flowfield. Predictions for engineering use, on the other hand, can be foreseen for sometime to come to depend upon modeling of selected features of turbulence at various levels of sophistication dictated by perceived need and available capability.
