Swirl-stabilized Lean-premixed Flame Combustion Dynamics: An Experimental Investigation of Flame Stabilization, Flame Dynamics and Combustion Instability Control Strategies PDF Download
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Author: Rajavasanth Rajasegar
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Rajavasanth Rajasegar
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Paul Palies
Publisher: Academic Press
ISBN: 0128199970
Category : Technology & Engineering
Languages : en
Pages : 402
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Book Description
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
Author: Uyi O. Idahosa
Publisher:
ISBN:
Category : Acoustic impedance
Languages : en
Pages : 161
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Book Description
The prevalence of gas turbines operating in primarily lean premixed modes is predicated on the need for lower emissions and increased efficiency. An enhancement in the mixing process through the introduction of swirl in the combustion reactants is also necessary for flame stabilization. The resulting lean swirling flames are often characterized by a susceptibility to feedback between velocity, pressure and heat release perturbations with a potential for unstable self-amplifying dynamics. The existing literature on combustion dynamics is predominantly dedicated to premixed flame configurations motivated by power generation and propulsive gas turbine applications. In the present research effort, an investigation into the response of atmospheric, non-premixed swirling flames to acoustic perturbations at various frequencies (f[subscript p] = 0-315Hz) and swirl intensities (S=0.09 and S=0.34) is carried out. The primary objective of the research effort is to broaden the scope of fundamental understanding in flame dynamics in the literature to include non-premixed swirling flames. Applications of the research effort include control strategies to mitigate the occurrence of combustion instabilities in future power generation gas turbines. Flame heat release is quantitatively measured using a photomultiplier with a 430nm bandpass filter for observing CH* chemiluminescence which is simultaneously imaged with a phase-locked CCD camera. Acoustic perturbations are generated with a loudspeaker at the base of an atmospheric co-flow burner with resulting velocity oscillation amplitudes, [vertical line]u'/U[subscript avg][vertical line] in the 0.03-0.30 range. The dependence of flame dynamics on the relative richness of the flame is investigated by studying various constant fuel flow rate flame configurations. The effect of varying fuel flow rates on the flame response is also examined using with dynamic time-dependent fuel supply rates over the data acquisition period. The Particle Image Velocimetry (PIV) method is used to study the isothermal flow field associated with acoustic pulsing. The acoustic impedance, wavelet analysis, Rayleigh criteria and phase conditioning methods are used to identify fundamental mechanisms common to highly responsive flame configurations.
Author: Yun Huang
Publisher:
ISBN:
Category : Combustion
Languages : en
Pages : 252
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Book Description
In a similar fashion, increasing the pressure was found to alter the flame shape and flame extent, but the thermo-acoustic coupling and induced large scale structure persisted to 0.34MPa, the highest pressure tested.
Author: Tim C. Lieuwen
Publisher: Cambridge University Press
ISBN: 1139576836
Category : Technology & Engineering
Languages : en
Pages : 427
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Book Description
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.
Author: Timothy C. Lieuwen
Publisher: AIAA (American Institute of Aeronautics & Astronautics)
ISBN:
Category : Science
Languages : en
Pages : 688
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Book Description
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.
Author: Zachary Alexander LaBry
Publisher:
ISBN:
Category :
Languages : en
Pages : 220
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Book Description
One of the most difficult challenges facing the development of modern gas turbines-for power generation, and propulsion-is the mitigation of dynamic instabilities in the presence of efficiency and emissions constraints. Dynamic instabilities-self-excited, self-sustaining oscillations which link the combustor acoustics to the combustion process-can result in significant levels of thermal and mechanical stress on combustion systems, leading to reduced operational lifetime, potentially dangerous failure modes, and significant deviations from the desired operating conditions. Due to the complexity of the problem, with the relevant time and length scales of the system--from the chemistry to the acoustics-spanning several orders of magnitude, even sophisticated numerical techniques have been severely limited in their ability to make reliable predictions, leaving the task of finding and eliminating modes of instability to a lengthy and expensive trial-and-error process. Lean-premixed combustion, one of the leading technologies for low emission combustors, is particularly susceptible to these types of instabilities. The sealed systems that are necessary to maintain a reaction in a lean mixture do not attenuate acoustics well, which often results in high-amplitude pressure fluctuations. In this thesis, we focus on developing a better predictive framework for the onset of combustion instabilities in a swirl-stabilized, lean-premixed combustor. We correlate the self-excited acoustic behavior with quantifiable system properties that can be generalized across different fuel blends. This work is predicated on the idea that self-excited combustion instability arises from the selective amplification of the noise inherent in a turbulent combustion system, and that the frequency-based response of the flame is a function of the flame geometry. In the first part of the thesis, we focus on the flame geometry, identifying several discrete transitions that take place in the swirl-stabilized flame as we adjust the equivalence ratio. By comparing the transitions across several CH4/H2 fuel blends, and using statistical techniques to interrogate the global effect of the small-scale flow-flame interactions, we find that the extinction strain rate-the flow-driven rate of change in flame surface area at which the chemistry is no longer -sufficiently fast to maintain the reaction-is directly linked to the flame transitions. The swirl-stabilized flow features several critical regions with large and unsteady velocity derivatives, particularly, a pair of shear layers that divide the incoming flow of reactants from an inner and an outer recirculation zone. As the extinction strain rate increases with increasing equivalence ratio, the flame transitions through these critical regions, manifesting as discrete changes in the flame geometry. In the second part, we address the correlation between self-excited instability and the forced acoustic response. By modifying the pressure boundary conditions, we decouple the flame from the acoustics over a domain of interest (defined by a range of equivalence ratios that correspond to the onset of dynamic instability in the coupled system). We then apply external acoustic forcing at a single frequency to ascertain the response of the flame to each particular forcing frequency by means of a flame transfer function. This enables us to consider the frequency-by-frequency response of the flame to its own internally generated noise. We show that the onset of instability is well-predicted by the overlap of the natural acoustic frequencies of the combustor (predicted using a non-linear flame response model) with those frequencies for which the phase of the flame transfer function satisfies the well-known Rayleigh criterion, which is a necessary condition for the presence of self-excited combustion instability. By examining both the forced response and the self-excited instability across several different fuel blends, we go on to show that both behaviors correlate well with the flame geometry, which we have already shown to be dictated by the extinction strain rate of the particular fuel blend. We go on to collapse both sets of data on the strained flame consumption speed taken at the limit of the extinction strain rate, and in doing so, present a framework for predicting the operating conditions under which the combustor in the coupled configuration will go unstable based on measurements and correlations from the uncoupled configuration. Furthermore by taking the consumption speed at the extinction limit, we are correlating the geometry and dynamics with a parameter that is solely a function of mixture properties. This provides the basis for a framework for predicting instability from properties that are more readily measured or simulated, and provides and explicit means of converting these results to different fuel mixtures.
Author: Medhat A. Nemitallah
Publisher: Springer Nature
ISBN: 303044077X
Category : Technology & Engineering
Languages : en
Pages : 426
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Book Description
This book focuses on the development of novel combustion approaches and burner designs for clean power generation in gas turbines. It shows the reader how to control the release of pollutants to the environment in an effort to reduce global warming. After an introduction to global warming issues and clean power production for gas turbine applications, subsequent chapters address premixed combustion, burner designs for clean power generation, gas turbine performance, and insights on gas turbine operability. Given its scope, the book can be used as a textbook for graduate-level courses on clean combustion, or as a reference book to accompany compact courses for mechanical engineers and young researchers around the world.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 1134
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Author: Nedunchezhian Swaminathan
Publisher: Cambridge University Press
ISBN: 1139498584
Category : Technology & Engineering
Languages : en
Pages : 447
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Book Description
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.
