Lean Blowout Dynamics For Premixed Bluff Body Flames

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Lean Blowout Dynamics for Premixed Bluff-body Flames

Author : Anthony J. Morales
Publisher :
ISBN 13 :
Total Pages : 84 pages
Book Rating : 4.:/5 (12 download)

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Book Synopsis Lean Blowout Dynamics for Premixed Bluff-body Flames by : Anthony J. Morales

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.

Flame Extinction Dynamics of Lean Premixed Bluff-body Stabilized Flames

Author : Marissa Kelley MacDonald
Publisher :
ISBN 13 :
Total Pages : 218 pages
Book Rating : 4.:/5 (894 download)

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Book Synopsis Flame Extinction Dynamics of Lean Premixed Bluff-body Stabilized Flames by : Marissa Kelley MacDonald

Download or read book Flame Extinction Dynamics of Lean Premixed Bluff-body Stabilized Flames written by Marissa Kelley MacDonald and published by . This book was released on 2014 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Stabilization and Dynamic of Premixed Swirling Flames

Author : Paul Palies
Publisher : Academic Press
ISBN 13 : 0128199970
Total Pages : 402 pages
Book Rating : 4.1/5 (281 download)

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Book Synopsis Stabilization and Dynamic of Premixed Swirling Flames by : Paul Palies

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

Advances in Turbulent Combustion Dynamics Simulations in Bluff-Body Stabilized Flames

Author : Jonathan Michael Tovar
Publisher :
ISBN 13 :
Total Pages : 89 pages
Book Rating : 4.:/5 (17 download)

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Book Synopsis Advances in Turbulent Combustion Dynamics Simulations in Bluff-Body Stabilized Flames by : Jonathan Michael Tovar

Download or read book Advances in Turbulent Combustion Dynamics Simulations in Bluff-Body Stabilized Flames written by Jonathan Michael Tovar and published by . This book was released on 2015 with total page 89 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work examines the three main aspects of bluff-body stabilized flames: stationary combustion, lean blow-out, and thermo-acoustic instabilities. For the cases of stationary combustion and lean blow-out, an improved version of the Linear Eddy Model approach is used, while in the case of thermo-acoustic instabilities, the effect of boundary conditions on the predictions are studied. The improved version couples the Linear Eddy Model with the full-set of resolved scale Large Eddy Simulation equations for continuity, momentum, energy, and species transport. In traditional implementations the species equations are generally solved using a Lagrangian method which has some significant limitations. The novelty in this work is that the Eulerian species concentration equations are solved at the resolved scale and the Linear Eddy Model is strictly used to close the species production term. In this work, the improved Linear Eddy Model approach is applied to predict the flame properties inside the Volvo rig and it is shown to over-predict the flame temperature and normalized velocity when compared to experimental data using a premixed single step global propane reaction with an equivalence ratio of 0.65. The model is also applied to predict lean blow-out and is shown to predict a stable flame at an equivalence ratio of 0.5 when experiments achieve flame extinction at an equivalence ratio of 0.55. The improved Linear Eddy Model is, however, shown to be closer to experimental data than a comparable reactive flow simulation that uses laminar closure of the species source terms. The thermo-acoustic analysis is performed on a combustor rig designed at the Air Force Research Laboratory. The analysis is performed using a premixed single step global methane reaction for laminar reactive flow and shows that imposing a non-physical boundary condition at the rig exhaust will result in the suppression of acoustic content inside the domain and can alter the temperature contours in non-physical ways. It can be concluded from this work that it is important to include the proper exhaust configuration for reacting thermo-acoustic calculations so that non-physical boundary conditions do not compromise the solution.

A Detailed Investigation of Bluff Body Stabilized Flames (Postprint).

Author :
Publisher :
ISBN 13 :
Total Pages : 12 pages
Book Rating : 4.:/5 (318 download)

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Book Synopsis A Detailed Investigation of Bluff Body Stabilized Flames (Postprint). by :

Download or read book A Detailed Investigation of Bluff Body Stabilized Flames (Postprint). written by and published by . This book was released on 2007 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reduced Order Models (ROMs) and Computational Fluid Dynamics (CFD) codes are tools used to predict the extinction of flames behind bluff bodies. Accurate prediction of these models and codes is predicated on their validation with experimental data. This paper describes detailed experiments to obtain validation data for bluff body stabilized flames over a wide range of conditions. Included are non-reacting data from CFD and LDV, lean blowout and high speed images for three different flame holders. In our previous paper (Kiel 2006) it was asserted that the large vortices were a major driver of extinction. Those assertions are further supported here. It is concluded that the vortex dynamics and not geometry is the dominant mechanism for bluff body flame extinction. This conclusion is supported by the lean blowout data, by the high speed images and reference data from NACA.

Unsteady Combustor Physics

Author : Tim C. Lieuwen
Publisher : Cambridge University Press
ISBN 13 : 1139576836
Total Pages : 427 pages
Book Rating : 4.1/5 (395 download)

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Book Synopsis Unsteady Combustor Physics by : Tim C. Lieuwen

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.

Turbulent Premixed Flames

Author : Nedunchezhian Swaminathan
Publisher : Cambridge University Press
ISBN 13 : 1139498584
Total Pages : 447 pages
Book Rating : 4.1/5 (394 download)

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Book Synopsis Turbulent Premixed Flames by : Nedunchezhian Swaminathan

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.

Investigation of Blowoff Mechanism and Forced Response of Bluff Body Stabilized Turbulent Premixed Flames

Author : Swetaprovo Chaudhuri
Publisher :
ISBN 13 :
Total Pages : 416 pages
Book Rating : 4.:/5 (712 download)

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Book Synopsis Investigation of Blowoff Mechanism and Forced Response of Bluff Body Stabilized Turbulent Premixed Flames by : Swetaprovo Chaudhuri

Download or read book Investigation of Blowoff Mechanism and Forced Response of Bluff Body Stabilized Turbulent Premixed Flames written by Swetaprovo Chaudhuri and published by . This book was released on 2010 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Turbulent Flame-vortex Dynamics of Bluff-body Premixed Flames

Author : Marissa Kelley Geikie
Publisher :
ISBN 13 :
Total Pages : 124 pages
Book Rating : 4.:/5 (15 download)

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Book Synopsis Turbulent Flame-vortex Dynamics of Bluff-body Premixed Flames by : Marissa Kelley Geikie

Download or read book Turbulent Flame-vortex Dynamics of Bluff-body Premixed Flames written by Marissa Kelley Geikie and published by . This book was released on 2018 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: Furthermore, a change in the relative balance of the combustion-induced vorticity mechanisms and turbulence energy transport occurs as a result of increasing the turbulence and pressure gradient.

LES of Bluff Body Stabilized Premixed and Partially Premixed Combustion

Author : Ionut Porumbel
Publisher : VDM Publishing
ISBN 13 : 9783836461153
Total Pages : 236 pages
Book Rating : 4.4/5 (611 download)

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Book Synopsis LES of Bluff Body Stabilized Premixed and Partially Premixed Combustion by : Ionut Porumbel

Download or read book LES of Bluff Body Stabilized Premixed and Partially Premixed Combustion written by Ionut Porumbel and published by VDM Publishing. This book was released on 2008 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main topic of this work is the study of the equivalence ratio effect on flame stability and dynamics in premixed and partially premixed flames by means of an LES algorithm able to handle the entire range of combustion regimes, with no ad-hoc adjustable parameters and able to respond automatically to variations in the inflow conditions.

Mechanisms of Flame Extinction for Bluff Body Stabilized Flames with Influences of Pressure Gradient Tailoring

Author : Anthony J. Morales
Publisher :
ISBN 13 :
Total Pages : 49 pages
Book Rating : 4.:/5 (15 download)

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Book Synopsis Mechanisms of Flame Extinction for Bluff Body Stabilized Flames with Influences of Pressure Gradient Tailoring by : Anthony J. Morales

Download or read book Mechanisms of Flame Extinction for Bluff Body Stabilized Flames with Influences of Pressure Gradient Tailoring written by Anthony J. Morales and published by . This book was released on 2018 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flame extinction continues to hinder the performance of combustion technologies used in propulsion systems and power generating turbomachinery. Within these applications, there is a crucial need to improve energy output while minimizing harmful environmental impacts. Lean combustion helps attain these goals by minimizing fuel costs and reducing NO[subscript x] emissions. However, operating at lean conditions increases the likelihood of flame extinction; the flame becomes more susceptible to hydrodynamic instabilities which can induce global blowout and termination of the combustion process. The work in this thesis is focused on identifying the mechanisms of flame extinction and controlling these mechanisms via pressure gradient tailoring. This is accomplished within a premixed blow-down combustion facility utilizing a bluff body flame stabilizer where flame extinction is induced by removing the flow of fuel into the reactant mixture. CH* chemiluminescence imaging and high-speed particle imaging velocimetry (PIV) are used to determine the flame boundary and resolve the reacting flow field, respectively. The mechanisms of flame extinction are attributed to the changing vorticity dynamics within the flow field as the equivalence ratio is reduced, which will directly influence the strain rate experienced by the flame. To influence these vorticity dynamics, the test section walls are manipulated to alter the downstream pressure gradients. It is determined that increasing the magnitude of the downstream pressure gradient increases the growth of the strain rate and vorticity experienced by the flame.

Stabilization of an Unconfined Flame by a Bluff Body

Author : Jean R. Hertzberg
Publisher :
ISBN 13 :
Total Pages : 298 pages
Book Rating : 4.:/5 (29 download)

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Book Synopsis Stabilization of an Unconfined Flame by a Bluff Body by : Jean R. Hertzberg

Download or read book Stabilization of an Unconfined Flame by a Bluff Body written by Jean R. Hertzberg and published by . This book was released on 1986 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Lean Blowout Mitigation in Swirl Stabilized Premixed Flames

Author : Shashvat Prakash
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (173 download)

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Book Synopsis Lean Blowout Mitigation in Swirl Stabilized Premixed Flames by : Shashvat Prakash

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.

The Development of a Correlation to Predict the Lean Blowout of Bluff Body Stabilized Flames with a Focus on Relevant Timescales and Fuel Characteristics

Download The Development of a Correlation to Predict the Lean Blowout of Bluff Body Stabilized Flames with a Focus on Relevant Timescales and Fuel Characteristics PDF Online Free

Author : Bethany C. Huelskamp
Publisher :
ISBN 13 :
Total Pages : 66 pages
Book Rating : 4.:/5 (874 download)

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Book Synopsis The Development of a Correlation to Predict the Lean Blowout of Bluff Body Stabilized Flames with a Focus on Relevant Timescales and Fuel Characteristics by : Bethany C. Huelskamp

Download or read book The Development of a Correlation to Predict the Lean Blowout of Bluff Body Stabilized Flames with a Focus on Relevant Timescales and Fuel Characteristics written by Bethany C. Huelskamp and published by . This book was released on 2013 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: In many high-speed reacting flows, a bluff body is used to locally slow the velocity and stabilize the flame. Gas turbine engines, both in ground-based industrial settings, as well as in aviation settings, utilize bluff body stabilized flames, often running at lean fuel-air ratios to extend the equipment's lifetime or to meet emissions regulations. However, running the equipment at a lean condition also puts the system at risk for lean blowout, which can result in facility inefficiencies, hardware damage, and a catastrophic reduction in aircraft performance. This thesis uses experimental data taken at the Air Force Research Laboratory, as well as data collected from a review of past literature, to develop a correlation to predict lean blowout using a least squares curve fit method. The laminar flame speed and ignition delay time were calculated for subsets of the data using the chemical kinetics software Cantera, and the results were incorporated into the correlations. The purpose of this effort was to provide an accurate, practical method of predicting lean blowout for designers and modelers, as well as to provide insight into the critical parameters and timescales that govern the blowout process by examining the significance of each parameter included in the correlation and the physical and chemical processes it may affect. The correlations presented in this thesis indicate that the lean blowout of bluff body stabilized flames is dependent on both the Damkohler number and the Lewis number. U/D is the inverse of the fluid mechanic timescale, likely that of the mixing time in the shear layer between the recirculation zone and the fresh reactants. Pressure, temperature, and the hydrogen to carbon ratio of the fuel all affect the reactivity of the mixture, contributing to the chemical timescale in the Damkohler number. The molecular weight of the fuel influences the mass diffusion, and thereby the Lewis number, of the fuel. As the Lewis number increases, various reaction rates, including the turbulent flame speed, decrease, also affecting the chemical timescale in the Damkohler number. The exact chemical timescale could not be determined from the laminar flame speed and ignition delay time data. A major contribution of this work is establishing the role that fuel characteristics play in the lean blowout process. Very little work has been done in the literature on fuel effects in the lean blowout of bluff body stabilized flames, but the correlation developed clearly shows that both the molecular weight and hydrogen to carbon ratio of the fuel influence the process.

Experimental Investigation of the Dynamics and Blowoff Characteristics of Bluff-body Stabilized 2D, V-Shaped Turbulent Premixed Flames with Different Gaseous Hydrocarbon Fuels

Download Experimental Investigation of the Dynamics and Blowoff Characteristics of Bluff-body Stabilized 2D, V-Shaped Turbulent Premixed Flames with Different Gaseous Hydrocarbon Fuels PDF Online Free

Author : Rishi Roy
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (119 download)

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Book Synopsis Experimental Investigation of the Dynamics and Blowoff Characteristics of Bluff-body Stabilized 2D, V-Shaped Turbulent Premixed Flames with Different Gaseous Hydrocarbon Fuels by : Rishi Roy

Download or read book Experimental Investigation of the Dynamics and Blowoff Characteristics of Bluff-body Stabilized 2D, V-Shaped Turbulent Premixed Flames with Different Gaseous Hydrocarbon Fuels written by Rishi Roy and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Thermoacoustic Instability

Author : R. I. Sujith
Publisher : Springer Nature
ISBN 13 : 3030811352
Total Pages : 484 pages
Book Rating : 4.0/5 (38 download)

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Book Synopsis Thermoacoustic Instability by : R. I. Sujith

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.

Turbulent Combustion

Author : Norbert Peters
Publisher : Cambridge University Press
ISBN 13 : 1139428063
Total Pages : 322 pages
Book Rating : 4.1/5 (394 download)

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Book Synopsis Turbulent Combustion by : Norbert Peters

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.