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Author : Assaad Rachid Masri
Publisher :
ISBN 13 :
Total Pages : 794 pages
Book Rating : 4.:/5 (22 download)
Download or read book Turbulence-chemistry Interactions in Nonpremixed Flames of Hydrocarbon Fuels written by Assaad Rachid Masri and published by . This book was released on 1987 with total page 794 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (455 download)
Download or read book Turbulence-Chemistry Models in Highly Strained Non-Premixed Flames written by and published by . This book was released on 1998 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: To allow implementation of chemical kinetic schemes of arbitrary complexity in computational design codes for gas-turbine combustion, a new microstructural turbulent combustion model was developed. The fine structure of turbulent combustion was represented by PSR (Perfectly Stirred Reactor) theory. The theory is the intense-combustion analog of flamelet theory. Residence times in the PSR were related to the scalar dissipation, and turbulence-chemistry interactions were closed by using the probability distribution function for scalar dissipation in a turbulent flow. Calculations compared very favorably with Raman data on temperature and species from three turbulent bluff-body stabilized laboratory flames: (i) a non-premixed CO/H2/N2-air flame, (ii) a non-premixed CH4/H2-air flame, and (iii) a premixed CH4-air flame. With this success, the model was applied to two practical combustors: (iv) an axially-staged combustion system which produces about half the NOx of a conventional combustor while offering greater operability, and operates in an unusual regime of turbulence-chemistry interactions, and (v) a conventional aircraft engine combustor. In the latter case, a kinetic scheme with over 121 species and 996 elementary reactions was demonstrated. In both cases, the calculated results agreed well with temperature and species data. The physical model developed here was used directly in the industry-standard pressure-corrected mean Navier-Stokes/assumed-shape pdf/k-epsilon type of CFD code, which affords significant geometric flexibility and rapid convergence for gas-turbine combustor flowfields.
Author : Norbert Peters
Publisher : Cambridge University Press
ISBN 13 : 1139428063
Total Pages : 322 pages
Book Rating : 4.1/5 (394 download)
Download or read book Turbulent Combustion written by Norbert Peters and published by Cambridge University Press. This book was released on 2000-08-15 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: The combustion of fossil fuels remains a key technology for the foreseeable future. It is therefore important that we understand the mechanisms of combustion and, in particular, the role of turbulence within this process. Combustion always takes place within a turbulent flow field for two reasons: turbulence increases the mixing process and enhances combustion, but at the same time combustion releases heat which generates flow instability through buoyancy, thus enhancing the transition to turbulence. The four chapters of this book present a thorough introduction to the field of turbulent combustion. After an overview of modeling approaches, the three remaining chapters consider the three distinct cases of premixed, non-premixed, and partially premixed combustion, respectively. This book will be of value to researchers and students of engineering and applied mathematics by demonstrating the current theories of turbulent combustion within a unified presentation of the field.
Author :
Publisher :
ISBN 13 :
Total Pages : 56 pages
Book Rating : 4.:/5 (227 download)
Download or read book Development and Assessment of Turbulence-Chemistry Models in Highly Strained Non-Premixed Flames written by and published by . This book was released on 1994 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this research is a quantitative understanding of turbulence-chemistry interactions as they pertain to combustion in aeropropulsion engines. The two principal classes of accomplishment are: (1) The first-ever stochastic joint velocity-composition pdf simulations of bluff-body stabilized flames, and comparison with Raman data on major species, temperature and mixture fraction (mean and rms quantities of each) in the same burner. Fuels have been CO/H2 mixtures (whose reduced chemistry is modeled with two compositional variables) and methane (five variables). This method of merging pdf transport and CFD codes can be used to combine the pdf model with any of the CFD codes used in design. There is thus a clear path for transitioning the results of the research. Remaining issues included (i) a chemistry scheme for jet fuels (not just CO/H2 and CH4), tested in turbulence and not only in the the laminar context. and (ii) more species and temperature data in the regime of high turbulence intensity, so that the model can be tested in the regime of real engines. (2) The "Partially Stirred Reactor" or PaSR model was developed toward the first two of these goals. The unsteady evolution of a full chemistry scheme is computed in the presence of turbulence of prescribed frequency. jg p.2.
Author : Nedunchezhian Swaminathan
Publisher : Cambridge University Press
ISBN 13 : 1139498584
Total Pages : 447 pages
Book Rating : 4.1/5 (394 download)
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.
Author :
Publisher :
ISBN 13 :
Total Pages : 8 pages
Book Rating : 4.:/5 (683 download)
Download or read book Multiscalar Measurements of Turbulence-chemistry Interactions in Nonpremixed Flames written by and published by . This book was released on 1995 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Selected results from experiments conducted over the past several years involving simultaneous multiscalar point measurements in turbulent nonpremixed flames are reviewed in this paper. In these experiments, spontaneous Raman scattering and Rayleigh scattering measurements of the major species and temperature were combined with laser-induced fluorescence measurements of minor species. The most important feature of these experiments is that they provide detailed data on the instantaneous relationships among species concentration, temperature, and derived scalar quantities that reflect the state of mixing or the progress of reaction. The data allow quantitative comparisons of the thermochemical states in turbulent flames with those in idealized representations, such as steady strained laminar flames, perfectly stirred reactors, or adiabatic equilibrium. The data may also be compared with results (measured or calculated) from unsteady laminar flames and from direct numerical simulations (DNS) of turbulent reacting flows. such comparisons provide insights into the fundamental nature of turbulence-chemistry interactions, and they allow one to examine the validity of some of the basic assumptions that turbulent combustion models are built upon. Furthermore, these data allow quantitative evaluations of the predictive accuracy, strengths, and limitations of a wide variety of combustions models.
Author : Kenneth Kuan-yun Kuo
Publisher : John Wiley & Sons
ISBN 13 : 111809929X
Total Pages : 914 pages
Book Rating : 4.1/5 (18 download)
Download or read book Fundamentals of Turbulent and Multiphase Combustion written by Kenneth Kuan-yun Kuo and published by John Wiley & Sons. This book was released on 2012-07-03 with total page 914 pages. Available in PDF, EPUB and Kindle. Book excerpt: Detailed coverage of advanced combustion topics from the author of Principles of combustion, Second Edition Turbulence, turbulent combustion, and multiphase reacting flows have become major research topics in recent decades due to their application across diverse fields, including energy, environment, propulsion, transportation, industrial safety, and nanotechnology. Most of the knowledge accumulated from this research has never been published in book form—until now. Fundamentals of Turbulent and Multiphase Combustion presents up-to-date, integrated coverage of the fundamentals of turbulence, combustion, and multiphase phenomena along with useful experimental techniques, including non-intrusive, laser-based measurement techniques, providing a firm background in both contemporary and classical approaches. Beginning with two full chapters on laminar premixed and non-premixed flames, this book takes a multiphase approach, beginning with more common topics and moving on to higher-level applications. In addition, Fundamentals of Turbulent and Multiphase Combustion: Addresses seven basic topical areas in combustion and multiphase flows, including laminar premixed and non-premixed flames, theory of turbulence, turbulent premixed and non-premixed flames, and multiphase flows Covers spray atomization and combustion, solid-propellant combustion, homogeneous propellants, nitramines, reacting boundary-layer flows, single energetic particle combustion, and granular bed combustion Provides experimental setups and results whenever appropriate Supported with a large number of examples and problems as well as a solutions manual, Fundamentals of Turbulent and Multiphase Combustion is an important resource for professional engineers and researchers as well as graduate students in mechanical, chemical, and aerospace engineering.
Author : Frédéric A. Maury
Publisher :
ISBN 13 :
Total Pages : 228 pages
Book Rating : 4.:/5 (318 download)
Download or read book Nonpremixed Flames in Stagnating Turbulence written by Frédéric A. Maury and published by . This book was released on 1992 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : M.Y. Hussaini
Publisher : Springer Science & Business Media
ISBN 13 : 1461228840
Total Pages : 668 pages
Book Rating : 4.4/5 (612 download)
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.
Author : Martin Schlatter
Publisher :
ISBN 13 :
Total Pages : 134 pages
Book Rating : 4.:/5 (838 download)
Download or read book Modelling of turbulence-chemistry interactions with respect to the NOx formation in turbulent non-premixed flames written by Martin Schlatter and published by . This book was released on 1996 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Paul A. Libby
Publisher :
ISBN 13 :
Total Pages : 12 pages
Book Rating : 4.3/5 (91 download)
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:
Author : Martin Schlatter (Ingenieur.)
Publisher :
ISBN 13 :
Total Pages : 134 pages
Book Rating : 4.:/5 (823 download)
Download or read book Modelling of Turbulence-chemistry Interactions with Respect to the NOx Formation in Turbulent Non-premixed Flames written by Martin Schlatter (Ingenieur.) and published by . This book was released on 1996 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Alessandro Parente
Publisher : Frontiers Media SA
ISBN 13 : 2889717003
Total Pages : 160 pages
Book Rating : 4.8/5 (897 download)
Download or read book MILD Combustion: Modelling Challenges, Experimental Configurations and Diagnostic Tools written by Alessandro Parente and published by Frontiers Media SA. This book was released on 2021-11-26 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : S. M. Correa
Publisher :
ISBN 13 :
Total Pages : 77 pages
Book Rating : 4.:/5 (227 download)
Download or read book Carbon Monoxide and Turbulence-Chemistry Interactions: Blowoff and Extinction of Turbulent Diffusion Flames written by S. M. Correa and published by . This book was released on 1987 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this program is to understand turbulence chemistry interactions in combustion up to and including localized extinction. Experimentally, pilot stabilized non premixed turbulent jet flames of selected mixtures are being studied under conditions conducive to strain-induced local extinction. Laser based techniques such as Raman scattering and Rayleigh scattering are employed. Analytically, models based on the asymptotically thin flamelet concept and on distributed reaction zone concepts are being assessed. A significant finding is that the popular contemporary view of a turbulent flame as an ensemble of asymptotically thin flamelets seems incorrect. Alternative mechanisms based on thick flamelets are proposed. The results include: (1) A complete re evaluation of Raman data showing significant corrections due to high temperature effects. Keywords: Turbulence chemistry interactions, Extinction, Blowoff, turbulent diffusion flames, Superequilibrium, Laser diagnostics.
Author : Eric M. Walters
Publisher :
ISBN 13 :
Total Pages : 123 pages
Book Rating : 4.:/5 (954 download)
Download or read book Stability and Liftoff of Non-premixed Large Hydrocarbon Flames in MILD Conditions written by Eric M. Walters and published by . This book was released on 2016 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Moderate or Intense Low-oxygen Dilution (MILD) combustion regime has received interest from the industrial furnace and gas turbine engine industries due to attractive properties of reduced NO[subscript x] emissions and high thermal efficiency. MILD combustion is characterized by low oxygen concentrations (i.e. 3%-9% by volume) and high reactant temperatures. A fundamental understanding of the physics governing MILD combustion is required to design effective practical combustion devices. While the physics relevant to MILD combustion of small hydrocarbon fuels such as methane and ethylene have been well-characterized, the behavior of large hydrocarbon fuels, such as Jet-A, have not. This is significant because many practical devices such as internal combustion engines and gas turbine engines are designed to operate using large hydrocarbon fuels. With this background and motivation, the focus of the current study was to understand the mechanisms governing stability and ignition of these flames in the MILD regime. To this end, a series of experimental and numerical studies were conducted to identify the physics governing lifted large hydrocarbon flames in the MILD regime. A jet in hot coflow (JHC) burner was used to stabilize a large hydrocarbon flame in a laboratory environment. The coflow used a premixed CH4/H2 secondary burner to provide an oxidizer stream at high temperature and with low oxygen concentration, which emulates MILD conditions. The coflow temperature was varied between 1300K and 1500K and the oxygen concentration was varied between 3% and 9% by volume. Three different large hydrocarbon fuels (i.e. Jet-A and two experimental fuels) were vaporized and issued into the hot coflow, with Reynolds numbers based on the inner jet diameter ranging from 3,750 to 10,000. The fuel jet exit temperature was varied from 525K to 625K. The liftoff heights of the resulting flames were measured using OH* chemiluminescence, as the flames were not always visible. Opposed flow laminar diffusion flames simulations were employed to determine how the interaction between chemistry and strain may affect flame stability. Ignition delay calculations were used to determine how ignition chemistry may affect flame liftoff without considering the effect of mixing. Several conclusions were made from the measurements and simulations. Oscillation of the instantaneous flame liftoff height was observed and was attributed to the cyclic advection of burned fluid downstream and the subsequent autoignition of unburned fluid. An increase in the fuel jet temperature was found to stabilize the flames closer to the jet exit, which was attributed to an increase in entrainment caused by higher fuel jet velocities. Flames in a coflow with 3% O2 at an exit temperature of 1300K were found to exhibit a decrease in liftoff height with increasing fuel jet Reynolds number. This counter-intuitive trend was not observed in flames burning in a coflow with higher temperatures or in coflows with higher O2 concentrations. The decrease in flame liftoff height with Reynolds number was attributed to the transport of formaldehyde into unburned mixture via the observed oscillations in the flame base. This conclusion was supported by both PLIF measurements performed by previous researchers on gaseous MILD flames and by numerical calculations. Opposed flame simulations indicated that formaldehyde production was increased with strain rate, which is analogous to an increase in the fuel jet velocity. Ignition delay calculations indicated that formaldehyde addition decreased ignition delay times, which results in lower flame liftoff heights. Opposed flow flame simulations indicated that the effect of changes in CH2O production was diminished at increased coflow oxygen levels (i.e. 6% and 9%) and elevated coflow temperatures (i.e. 1400K and 1500K) due to lower formaldehyde production.
Author : S. M. Correa
Publisher :
ISBN 13 :
Total Pages : 78 pages
Book Rating : 4.:/5 (227 download)
Download or read book Carbon Monoxide and Turbulence-Chemistry Interactions: Blowoff and Extinction of Turbulent Jet Diffusion Flames written by S. M. Correa and published by . This book was released on 1988 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence chemistry interactions have been studied experimentally and theoretically in the context of turbulent diffusion flames. The goal is a quantitative understanding of these interactions under a wide range of conditions. These range from low Reynolds number conditions ('weak' interactions, affecting primarily the levels of intermediate species, pollutants and combustion efficiency) to high Reynolds number conditions, where the flame can be extinguished by intense turbulent straining. Jet flames in coflowing air have been emphasized, with a coannular pilot burner used where necessary for stabilization at the burner lip. Fuels have consisted of carbon dioxide/H2 mixtures with the fraction of hydrogen successively reduced to promote extinction. Reynolds numbers have been increased to the point of blowoff. Major species and temperature have been measured by Raman scattering, and velocity and turbulence have been measured by laser velocimetry. These experiments have provided a comprehensive set of data on CO/H2 flames, extending to conditions conducive to localized extinction. The data show significant temperature decrements due to finite-rate chemistry but no evidence of localized extinction. Keywords: Turbulence, Chemistry interactions, Extinction, Turbulent diffusion flames, Superequilibrium, Laser diagnostics. (MJM).
Author :
Publisher :
ISBN 13 :
Total Pages : 5 pages
Book Rating : 4.:/5 (727 download)
Download or read book Non-premixed Flame-turbulence Interaction in Compressible Turbulent Flow written by and published by . This book was released on 2002 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nonpremixed turbulent reacting flows are intrinsically difficult to model due to the strong coupling between turbulent motions and reaction. The large amount of heat released by a typical hydrocarbon flame leads to significant modifications of the thermodynamic variables and the molecular transport coefficients and thus alters the fluid dynamics. Additionally, in nonpremixed combustion, the flame has a complex spatial structure. Localized expansions and contractions occur, enhancing the dilatational motions. Therefore, the compressibility of the flow and the heat release are intimately related. However, fundamental studies of the role of compressibility on the scalar mixing and reaction are scarce. In this paper they present results concerning the fundamental aspects of the interaction between non-premixed flame and compressible turbulence.
