Download or read book On the Lean Blowout Limit of Premixed Flames written by E. Gutmark and published by . This book was released on 1989 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Lean Blowout Mitigation in Swirl Stabilized Premixed Flames written by Shashvat Prakash and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Lean, premixed combustion offers a practical approach for reducing nitrogen oxide (NOx) emissions, but increases the risk of lean blowout (LBO) in gas turbines. Active control techniques are therefore sought which can stabilize a lean flame and prevent LBO. The present work has resulted in the development of flame detection, dynamic modeling, blowout margin estimation, and actuation and control techniques. The flame's acoustic emissions were bandpass filtered at select frequencies to detect localized extinction events, which were found to increase in number near LBO. The lean flame was also found to intermittently burst into a transient 'tornado' configuration in which the flame's inner recirculation zone would collapse. The localized extinctions were dynamically linked to the tornado bursts using a linear, first order model. The model was subsequently applied to predict tornado bursts based on optically detected localized extinction events. It was found that both localized extinctions and tornado bursts are by themselves Poisson processes; the exponential distribution of their spacing times could be used to determine blowout probability. Blowout mitigation was achieved by redistributing the fuel flow between the annular swirlers and central preinjection pilot, both of which were premixed. Rule-based and lead-lag control architectures were developed and validated.
Download or read book Establishing Flashback and Blowout Limits in a Commercial Lean Premixed Combustor Operating on Synthesis Gas written by David Page and published by . This book was released on 2012 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flashback and lean blowout are operability issues that must be addressed for successful operation of stationary gas turbines. The present work focuses on flashback and lean blowout of premixed jet flames in a combustor from a commercially available gas turbine operating on synthesis gas of various compositions. The issues of flashback and lean blowout are exacerbated when operating on fuels with high hydrogen content due to the increased reactivity of hydrogen, thus increasing the propensity for flashback. Operating margins for mixtures of natural gas (NG) and carbon monoxide (CO) in hydrogen (H2) are reported. The results demonstrate less stability near lean blowout for mixtures of H2/NG than for H2/CO. Increasing H2 concentration extends the lean operating limit from [phi] = 0.63 to [phi] = 0.29 for H2/NG and [phi] = 0.42 to [phi] = 0.29 for H2/CO. Modeling of the experimental data using a perfectly stirred reactor indicates that the Damköhler number well characterizes the effects of the addition of H2 to NG on the lean blowout limits. In addition, key factors dominating flashback behavior are identified and included in a predictive methodology. A response surface, developed from a turbulent flame speed database, is used to create a flashback propensity index as a design tool for quantifying flashback based upon experimental data from the combustor. Furthermore, the Damköhler number is explored as an index for predicting flashback and was determined to be effective at capturing the effect of pressure, making it able to link data taken at atmospheric conditions to expected engine results.
Download or read book Premixing Quality and Flame Stability written by Krishnan Radhakrishnan and published by . This book was released on 1979 with total page 72 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 Unsteady Combustor Physics written by Tim C. Lieuwen and published by Cambridge University Press. This book was released on 2012-08-27 with total page 427 pages. Available in PDF, EPUB and Kindle. Book excerpt: Developing clean, sustainable energy systems is a pre-eminent issue of our time. Most projections indicate that combustion-based energy conversion systems will continue to be the predominant approach for the majority of our energy usage. Unsteady combustor issues present the key challenge associated with the development of clean, high-efficiency combustion systems such as those used for power generation, heating or propulsion applications. This comprehensive study is unique, treating the subject in a systematic manner. Although this book focuses on unsteady combusting flows, it places particular emphasis on the system dynamics that occur at the intersection of the combustion, fluid mechanics and acoustic disciplines. Individuals with a background in fluid mechanics and combustion will find this book to be an incomparable study that synthesises these fields into a coherent understanding of the intrinsically unsteady processes in combustors.
Download or read book Lean Blowout Dynamics for Premixed Bluff body Flames written by Anthony J. Morales and published by . This book was released on 2020 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lean blowout is experimentally investigated for premixed bluff-body flames under various inlet velocity conditions, pressure gradients, and turbulence conditions to study the influence of fluid mechanics on the lean blowout process. A premixed combustion facility paired with a bluff-body flame stabilizer is used for the study. For all experiments, lean blowout is induced by temporally decreasing the fuel flow rate into the reactant stream. A suite of high-speed optical diagnostics are simultaneously employed to capture the transient blowout process: particle image velocimetry (PIV), stereoscopic PIV, and C2*/CH* chemiluminescence imaging. These diagnostics allow for the instantaneous flame boundary, velocity fields, equivalence ratios, and local flame strain rates to be evaluated during blowout. For all testing conditions, the results show that the blowout process is highly coupled to the fluid mechanics within the reacting domain and blowout is driven from flame-flow interactions (i.e. flame-vorticity interactions or flame-turbulence interactions). The results also demonstrate that altering the vorticity dynamics or turbulence conditions within the reacting domain can profoundly augment or attenuate the blowout process.
Download or read book Studies on Lean blowout Characteristics of a Premixed Jet Flame written by Viswanath R. Katta and published by . This book was released on 1995 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presented at the International Gas Turbine and Aeroengine Congress and Exposition, Houston, Texas - June 5-8, 1995.
Download or read book Thermoacoustic Instability written by R. I. Sujith and published by Springer Nature. This book was released on 2021-12-14 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book systematically presents the consolidated findings of the phenomenon of self-organization observed during the onset of thermoacoustic instability using approaches from dynamical systems and complex systems theory. Over the last decade, several complex dynamical states beyond limit cycle oscillations such as quasiperiodicity, frequency-locking, period-n, chaos, strange non-chaos, and intermittency have been discovered in thermoacoustic systems operated in laminar and turbulent flow regimes. During the onset of thermoacoustic instability in turbulent systems, an ordered acoustic field and large coherent vortices emerge from the background of turbulent combustion. This emergence of order from disorder in both temporal and spatiotemporal dynamics is explored in the contexts of synchronization, pattern formation, collective interaction, multifractality, and complex networks. For the past six decades, the spontaneous emergence of large amplitude, self-sustained, tonal oscillations in confined combustion systems, characterized as thermoacoustic instability, has remained one of the most challenging areas of research. The presence of such instabilities continues to hinder the development and deployment of high-performance combustion systems used in power generation and propulsion applications. Even with the advent of sophisticated measurement techniques to aid experimental investigations and vast improvements in computational power necessary to capture flow physics in high fidelity simulations, conventional reductionist approaches have not succeeded in explaining the plethora of dynamical behaviors and the associated complexities that arise in practical combustion systems. As a result, models and theories based on such approaches are limited in their application to mitigate or evade thermoacoustic instabilities, which continue to be among the biggest concerns for engine manufacturers today. This book helps to overcome these limitations by providing appropriate methodologies to deal with nonlinear thermoacoustic oscillations, and by developing control strategies that can mitigate and forewarn thermoacoustic instabilities. The book is also beneficial to scientists and engineers studying the occurrence of several other instabilities, such as flow-induced vibrations, compressor surge, aeroacoustics and aeroelastic instabilities in diverse fluid-mechanical environments, to graduate students who intend to apply dynamical systems and complex systems approach to their areas of research, and to physicists who look for experimental applications of their theoretical findings on nonlinear and complex systems.
Download or read book Stabilization and Dynamic of Premixed Swirling Flames written by Paul Palies and published by Academic Press. This book was released on 2020-07-03 with total page 402 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stabilization and Dynamic of Premixed Swirling Flames: Prevaporized, Stratified, Partially, and Fully Premixed Regimes focuses on swirling flames in various premixed modes (stratified, partially, fully, prevaporized) for the combustor, and development and design of current and future swirl-stabilized combustion systems. This includes predicting capabilities, modeling of turbulent combustion, liquid fuel modeling, and a complete overview of stabilization of these flames in aeroengines. The book also discusses the effects of the operating envelope on upstream fresh gases and the subsequent impact of flame speed, combustion, and mixing, the theoretical framework for flame stabilization, and fully lean premixed injector design. Specific attention is paid to ground gas turbine applications, and a comprehensive review of stabilization mechanisms for premixed, partially-premixed, and stratified premixed flames. The last chapter covers the design of a fully premixed injector for future jet engine applications. Features a complete view of the challenges at the intersection of swirling flame combustors, their requirements, and the physics of fluids at work Addresses the challenges of turbulent combustion modeling with numerical simulations Includes the presentation of the very latest numerical results and analyses of flashback, lean blowout, and combustion instabilities Covers the design of a fully premixed injector for future jet engine applications
Download or read book Flashback Mechanisms in Lean Premixed Gas Turbine Combustion written by Ali Cemal Benim and published by Academic Press. This book was released on 2014-12-01 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Blending fuels with hydrogen offers the potential to reduce NOx and CO2 emissions in gas turbines, but doing so introduces potential new problems such as flashback. Flashback can lead to thermal overload and destruction of hardware in the turbine engine, with potentially expensive consequences. The little research on flashback that is available is fragmented. Flashback Mechanisms in Lean Premixed Gas Turbine Combustion by Ali Cemal Benim will address not only the overall issue of the flashback phenomenon, but also the issue of fragmented and incomplete research. Presents a coherent review of flame flashback (a classic problem in premixed combustion) and its connection with the growing trend of popularity of more-efficient hydrogen-blend fuels Begins with a brief review of industrial gas turbine combustion technology Covers current environmental and economic motivations for replacing natural gas with hydrogen-blend fuels
Download or read book Fundamentals of Combustion Processes written by Sara McAllister and published by Springer Science & Business Media. This book was released on 2011-05-10 with total page 315 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamentals of Combustion Processes is designed as a textbook for an upper-division undergraduate and graduate level combustion course in mechanical engineering. The authors focus on the fundamental theory of combustion and provide a simplified discussion of basic combustion parameters and processes such as thermodynamics, chemical kinetics, ignition, diffusion and pre-mixed flames. The text includes exploration of applications, example exercises, suggested homework problems and videos of laboratory demonstrations
Download or read book Combustion Noise written by Anna Schwarz and published by Springer Science & Business Media. This book was released on 2009-06-17 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: November, 2008 Anna Schwarz, Johannes Janicka In the last thirty years noise emission has developed into a topic of increasing importance to society and economy. In ?elds such as air, road and rail traf?c, the control of noise emissions and development of associated noise-reduction techno- gies is a central requirement for social acceptance and economical competitiveness. The noise emission of combustion systems is a major part of the task of noise - duction. The following aspects motivate research: • Modern combustion chambers in technical combustion systems with low pol- tion exhausts are 5 - 8 dB louder compared to their predecessors. In the ope- tional state the noise pressure levels achieved can even be 10-15 dB louder. • High capacity torches in the chemical industry are usually placed at ground level because of the reasons of noise emissions instead of being placed at a height suitable for safety and security. • For airplanes the combustion emissions become a more and more important topic. The combustion instability and noise issues are one major obstacle for the introduction of green technologies as lean fuel combustion and premixed burners in aero-engines. The direct and indirect contribution of combustion noise to the overall core noise is still under discussion. However, it is clear that the core noise besides the fan tone will become an important noise source in future aero-engine designs. To further reduce the jet noise, geared ultra high bypass ratio fans are driven by only a few highly loaded turbine stages.
Download or read book The Behavior of Fuel lean Premixed Flames in a Standard Flammability Limit Tube Under Controlled Gravity Conditions written by Brian Leigh Wherley and published by . This book was released on 1986 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Combustion Instabilities in Gas Turbine Engines written by Timothy C. Lieuwen and published by AIAA (American Institute of Aeronautics & Astronautics). This book was released on 2005 with total page 688 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers gas turbine users and manufacturers a valuable resource to help them sort through issues associated with combustion instabilities. In the last ten years, substantial efforts have been made in the industrial, governmental, and academic communities to understand the unique issues associated with combustion instabilities in low-emission gas turbines. The objective of this book is to compile these results into a series of chapters that address the various facets of the problem. The Case Studies section speaks to specific manufacturer and user experiences with combustion instabilities in the development stage and in fielded turbine engines. The book then goes on to examine The Fundamental Mechanisms, The Combustor Modeling, and Control Approaches.
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.
Download or read book Lean Premixed Flames for Low NO subscript X Combustors written by and published by . This book was released on 1995 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall objectives of the research at Purdue are to: obtain a reduced mechanism description of high pressure NO formation chemistry using experiments and calculations for laminar lean premixed methane air flames, develop a statistical model of turbulence NO chemistry interactions using a Bunsen type jet flame, and utilize the high pressure chemistry and turbulence models in a commercial design code, then evaluate its predictions using data from an analog gas turbine combustor. Work to date has resulted in the following achievements: spatially resolved measurements of NO in high-pressure high-temperature flat flames, plus evaluation of the influence of flame radiation on the measured temperature profile; measurements of temperature and velocity PDFs for a turbulent methane/air flame were obtained for the first time, under operating conditions which allow their study in the distributed regimes, and the increase in EINO(subscript x) with equivalence ratio predicted using a chemical kinetics model; and simulation of non-reacting combustor flow fields from ambient to elevated pressure and temperature conditions and comparison of those results with experimental velocity profiles.
