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Blowoff Behavior Of Bluff Body Stabilized Flames In Vitiated And Partially Premixed Flows
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Book Synopsis Blowoff Behavior of Bluff Body Stabilized Flames in Vitiated and Partially Premixed Flows by : Steven G. Tuttle
Download or read book Blowoff Behavior of Bluff Body Stabilized Flames in Vitiated and Partially Premixed Flows written by Steven G. Tuttle and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Optical Analysis of the Blowoff Behavior for Bluff Body-stabilized Flames in Vitiated Flow by : Trevor Ray Jensen
Download or read book An Optical Analysis of the Blowoff Behavior for Bluff Body-stabilized Flames in Vitiated Flow written by Trevor Ray Jensen and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Optical Analysis of the Blowoff Behavior for Bluff Body-stabilized Flames in Vitiated Flow by : Trevor Ray Jensen
Download or read book An Optical Analysis of the Blowoff Behavior for Bluff Body-stabilized Flames in Vitiated Flow written by Trevor Ray Jensen and published by . This book was released on 2011 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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:
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:
Book Synopsis BLOWOFF CHARACTERISTICS IN INTERACTING PREMIXED V-FLAMES. by : Joseph Crane
Download or read book BLOWOFF CHARACTERISTICS IN INTERACTING PREMIXED V-FLAMES. written by Joseph Crane and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
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.
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:
Book Synopsis Experimental Investigation on the Effects of Free Stream Turbulence and Fuel Type on Structure and Blowoff Characteristics of Turbulent Premixed Bluff-body Stabilized Flames by : Bikram Roy Chowdhury
Download or read book 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 published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
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
Book Synopsis Characteristic Time Correlation for Lean Blowoff of Bluff-Body-Stabilized Flames by : S. L. Plee
Download or read book Characteristic Time Correlation for Lean Blowoff of Bluff-Body-Stabilized Flames written by S. L. Plee and published by . This book was released on 1978 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Analysis of Blowoff Scaling of Bluff Body Stabilized Flames by : Sajjad A. Husain
Download or read book Analysis of Blowoff Scaling of Bluff Body Stabilized Flames written by Sajjad A. Husain and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Bluff body stabilization of flames is a commonly employed technique for combustion applications, such as thrust augmentors. These combustors are usually required to operate at lean conditions governed by a lower stability limit on combustion denoted by lean blow off. Lean blow off is believed to be a dynamically unstable phenomenon that leads to flame extinction or convection from a stable, usually desired, point in space. Current theories predict lean blow off based on models that were developed over specific domain of inflow parameters. This thesis sought to compile, re-evaulate, and analyze past blowoff data presented in literature using time scale correlations, Damkohler numbers, by employing modern chemical kinetic solvers to approximate characteristic chemical times. The research has conclusively shown that it is possible to express blowoff data for multiple flow conditions using a power law relationship between Damkohler number and Reynolds numbers. From the analysis of this power law relations, trends are validated using past empirical observations, and some new information regarding flame stability is also conveyed.
Book Synopsis Phase-resolved Characterization of Conical Turbulent Premixed Flames by : Sayan Biswas
Download or read book Phase-resolved Characterization of Conical Turbulent Premixed Flames written by Sayan Biswas and published by . This book was released on 2012 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Book Synopsis Experimental Investigation Into Thermo-Acoustic Instability in Pre-Mixed, Pre-Vaporized Bluff-Body Stabilized Flames by : Jeffrey Ross Monfort
Download or read book Experimental Investigation Into Thermo-Acoustic Instability in Pre-Mixed, Pre-Vaporized Bluff-Body Stabilized Flames written by Jeffrey Ross Monfort and published by . This book was released on 2015 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
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:
Book Synopsis Direct Numerical Simulation of Bluff-body Stabilized Flames by : Farzin Jalilalghadr
Download or read book Direct Numerical Simulation of Bluff-body Stabilized Flames written by Farzin Jalilalghadr and published by . This book was released on 2007 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct numerical simulation (DNS) is used to study reacting and non-reacting bluff-body stabilized flows. Three fuel-to-air velocity ratios were considered. The results show that three types of flow fields can be identified. For the fuel-to-air velocity ratio of 0:84, the flow field is dominated by the reverse flow of the coflowing air. The jet does not penetrate through the reverse flow, and two stagnation points are formed on the centerline, where the jet and air stagnate. The downstream flow field is similar to a wake flow, and therefore this flow is referred to as a bluff-body dominant flow. For the fuel-to-air velocity ratio of 1:4, the flow field is neither dominated by the jet nor the coflowing air and is referred to as an intermittent flow. For the fuel-to-air velocity ratio of 2:8, the jet penetrates through the reverse flow and no stagnation point is formed. The flow field is similar to that of a pure jet, therefore this flow is referred to as a jet dominant flow. In all cases, the coflowing air converges towards the centerline and forms a recirculation zone that extends to approximately one bluff-body diameter downstream. For the reacting flow, the methane combustion is modeled via a global, 1-step kinetic mechanism. The main effects of combustion on the flow field are an increase in the length of the recirculation zone, and a decrease in the velocity fluctuations. Based on the three velocity ratios, three types of flames are produced. For the velocity ratio of 0:84, a short mushroom shaped flame is produced near the fuel stagnation point. For the velocity ratio of 1:4, a medium length flame is produced in the shear layer region between the fuel and air. The flame is anchored in the recirculation zone, and extends downstream of the bluff-body. For the velocity ratio of 2:8, a long flame is produced near the centerline and is also anchored in the recirculation zone. All three flames are stabilized between the coflowing air and the jet, where the strain-rates are low, and the mixture fraction is near the stoichiometric value for methane combustion.
