Experimental Investigation Of The Dynamics And Blowoff Characteristics Of Bluff Body Stabilized 2d V Shaped Turbulent Premixed Flames With Different Gaseous Hydrocarbon Fuels

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Experimental Investigation Of The Dynamics And Blowoff Characteristics Of Bluff Body Stabilized 2d V Shaped Turbulent Premixed Flames With Different Gaseous Hydrocarbon Fuels

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Author : Rishi Roy
language : en
Publisher:
Release Date : 2018

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 has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with Electronic dissertations categories.

Experimental Investigation On The Effects Of Free Stream Turbulence And Fuel Type On Structure And Blowoff Characteristics Of Turbulent Premixed Bluff Body Stabilized Flames

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Author : Bikram Roy Chowdhury
language : en
Publisher:
Release Date : 2017

Experimental Investigation On The Effects Of Free Stream Turbulence And Fuel Type On Structure And Blowoff Characteristics Of Turbulent Premixed Bluff Body Stabilized Flames written by Bikram Roy Chowdhury and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with Electronic dissertations categories.

An experimental investigation on the effect of different levels of turbulence intensity and properties of the fuel/air mixture on the structure and characteristics of lean flames stabilized on an axisymmetric bluff body is described in this thesis. Simultaneous imaging of hydroxyl (OH) and formaldehyde (CH2O) by planar laser induced fluorescence and particle image velocimetry (PIV) were used to study the interaction between the flame and the flow field. CH2O fluorescence and the pixel-by-pixel multiplication of OH and CH2O fluorescence signals were utilized to mark preheat and heat release regions respectively. In addition, high-speed chemiluminescence imaging was performed to understand the time resolved characteristics of the flame. The first part of the thesis focuses on the characteristics of stably burning lean methane/-, propane/- and ethylene/air flames when subjected to low (4 %), moderate (14 %) and intense (24 and 30%) levels of free stream turbulence. The flame front structure was observed to be strongly dependent on the free stream turbulence level of the incoming fuel/air mixture as well on the properties of the fuel/air mixture. Formation of cusps and unburnt mixture fingers were observed as the turbulence intensity was increased from 4 to 14 % but, the heat release region remained continuous. Under intense turbulence conditions, methane/- and ethylene/air (f = 0.85) flames exhibited localized extinctions along the flame sheet and flamelet merging events which created isolated pockets of reactants in the flame envelope. In addition to these features, propane/- and ethylene/air (f=0.655) flames exhibited the occurrence of flame fragmentation events and the general shape of these flames were observed to intermittently switch from a symmetric (varicose) to asymmetric (sinuous) mode. Several properties were measured to characterize the effects of turbulence – flame interaction which includes the average preheat and reaction zone thicknesses, strain rates and curvature along the flame front, burning fraction, flame brush thickness, flame surface density, area ratio and turbulent flame speed. The next part of the thesis focuses on blowoff dynamics of lean methane/-, propane/- and ethylene/air flames for mean velocities of 5, 10 and 15 m/s and subjected to free stream turbulence levels from 4 to 30%. Apart from the propane/air flames at an apporach velcoity of 5 m/s and turbulence intensity of 30 %, increasing turbulence intensity was found to reduce the flame stability. The blowoff equivalence ratios of propane/air flames was observed to be higher than methane/- and ethylene/air flames. As blowoff was approached, the flame front and shear layer vortices entangled inducing high local strain rates on the flame front that exceed the extinction strain rate resulting in significant breaks along the reaction zone. At conditions near blowoff, significant increase in the frequency of breaks along the reaction zone was observed for low and moderate turbulence conditions. For the higher turbulence conditions, fragmentation of the flame along with the presence of sinuous wakes was observed which aided in the penetration of reactants into the recirculation zone. Velocity vectors near the flame holes indicate the penetration of the reactants into the recirculation zone. Mostly similar sequence of events was observed for methane/-, propane/- and ethylene/air flames near blowoff. Several properties weremeasured to characterize the near blowoff flames which include the strain rate and curvature statistics along the flame front, burning fraction, asymmetric index and the average duration of the blowoff event. Based on the observation from the experiments, turbulent flame speed was attributed to be the primary factor in governing the blowoff equivalence ratio. This point of view was examined by comparing the mean strain rate of methane/- and ethylene/air flames at the equivalence ratio corresponding to near blowoff for propane/air flames.

Investigation Of Blowoff Mechanism And Forced Response Of Bluff Body Stabilized Turbulent Premixed Flames

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Author : Swetaprovo Chaudhuri
language : en
Publisher:
Release Date : 2010

Investigation Of Blowoff Mechanism And Forced Response Of Bluff Body Stabilized Turbulent Premixed Flames written by Swetaprovo Chaudhuri and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.

Blowoff Characteristics In Interacting Premixed V Flames

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Author : Joseph Crane
language : en
Publisher:
Release Date : 2015

Blowoff Characteristics In Interacting Premixed V Flames written by Joseph Crane and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.

Flame interaction is a common phenomenon in many common combustion applications thatcan have a leading order effect on flame stabilization. In particular, flame stabilization is a key performance metric in low-emissions gas turbine engines for both aircraft and power generation applications. In this study, we explore the impact flame interaction on blowoff characteristics and flame shape on three two-dimensional bluff-body stabilized flames by varying the spacing between the bluff bodies and the velocity of the incoming flow. Flame locations are extracted from particle image velocimetry (PIV) data to study the differences in blowoff limits between two different bluff-body spacing configurations all at the same entering bulk flow velocity. Increasing the flame spacing led to wider flamesand less interaction. Geometric and flow profile effects are discussed with respect to flame interaction and blowoff phenomena.

Blowoff Behavior Of Bluff Body Stabilized Flames In Vitiated And Partially Premixed Flows

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Author : Steven G. Tuttle
language : en
Publisher:
Release Date : 2010

Blowoff Behavior Of Bluff Body Stabilized Flames In Vitiated And Partially Premixed Flows written by Steven G. Tuttle and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.

Lean Blowout Dynamics For Premixed Bluff Body Flames

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Author : Anthony J. Morales
language : en
Publisher:
Release Date : 2020

Lean Blowout Dynamics For Premixed Bluff Body Flames written by Anthony J. Morales and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with categories.

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.

Phase Resolved Characterization Of Conical Turbulent Premixed Flames

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Author : Sayan Biswas
language : en
Publisher:
Release Date : 2012

Phase Resolved Characterization Of Conical Turbulent Premixed Flames written by Sayan Biswas and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.

Turbulent Premixed Flames

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Author : Nedunchezhian Swaminathan
language : en
Publisher: Cambridge University Press
Release Date : 2011-04-25

Turbulent Premixed Flames written by Nedunchezhian Swaminathan and has been published by Cambridge University Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011-04-25 with Technology & Engineering categories.

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.

Experimental Investigation Into Thermo Acoustic Instability In Pre Mixed Pre Vaporized Bluff Body Stabilized Flames

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Author : Jeffrey Ross Monfort
language : en
Publisher:
Release Date : 2015

Experimental Investigation Into Thermo Acoustic Instability In Pre Mixed Pre Vaporized Bluff Body Stabilized Flames written by Jeffrey Ross Monfort and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.

An experimental campaign was undertaken to investigate the thermo-acoustic properties of a bluff-body stabilized flame in an atmospheric pressure facility at the Air Force Research Laboratory. Of particular interest were the possible interactions between the acoustic properties of the test rig, the vortex shedding due to the presence of the bluff-body, and the unsteady heat release within the chamber. An analysis of the vortex shedding modes due to the bluff-body and the acoustic modes indicated that there are regions in the operating envelope where the two mode types share similar frequencies given an operating condition, creating a scenario where feedback might be possible. Further investigation into the fluctuating velocity components in the wake of the bluff-body indicated that the Strouhal number is not single-valued, and that vortices of varying sizes, and accompanying characteristic frequencies, are shed from a single bluff-body.With previous research indicating that lean blow-off is preceded by local extinctions within the reaction zone, and blow-off being closely related to the ratio of chemical and fluidic time scales, an experiment was conducted to determine whether or not flames undergoing thermo-acoustic instability also exhibit regions of decreased residence time. This experiment concluded that the regions of acoustically-coupled flames which undergo large-scale oscillations do, in fact, correlate with decreased residence time. This conclusion links both lean static stability and near-stoichiometric dynamic stability to simple time scales prescribed by vortex behavior in the wake of a bluff-body.An investigation was conducted which utilized simultaneous high-speed particle image velocimetry (PIV), planar laser-induced fluorescence (PLIF) and pressure measurements in the near-wake region of a bluff-body stabilized flame. In addition to the simultaneous measurements listed, high-speed broadband chemiluminescence was also collected. The 2-D nature of these measurements led to their analysis through the utilization of proper orthogonal decomposition (POD). The decomposition of the highly-complicated data sets allowed the dominant features to be extracted. These dominant features, in an acoustically-coupled flame, show remarkable symmetry that is not readily apparent in uncoupled flames. Further analysis of an objective measure of the flame symmetry as a function of equivalence ratio indicated that the fluctuations in the axial component of velocity best correlate with overall sound pressure level. This correlation indicates that the feedback interactions are based around the longitudinal acoustic modes of the combustion chamber.

International Aerospace Abstracts

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Author :
language : en
Publisher:
Release Date : 1997

International Aerospace Abstracts written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1997 with Aeronautics categories.